feat(gui): dsh-client-hmr reload driver and the dshClient-discovered watch-build script

client-hmr is a normal plugin package composed into dev graphs only. It
listens on /plugins/events and reloads one plugin per rebuilt frame,
serialized: invalidate, prefetch (fresh factory registers while the old
fiber still serves), registry.delete before touching the fiber, drain
disposers, drop owned style tags, entry.refresh(), fiber.await() loud.
Dependency cascade costs zero client code — fiber activation epochs
re-load dependents through cordis itself. Reload is coarse by design;
no rollback in v1; self-reload works with a frame gap the next rebuild
heals.

scripts/dev-web.ts (pnpm run dev:web) is the convenience watch-build:
it discovers its package list by scanning packages/*/*/package.json for
dshClient platform "web" at startup — no hardcoded roster — and talks
no protocol to the host. Gate bookkeeping rides along: knip entries for
the new packages, README model-experience allowlist rows.

packages/client/hmr/src/client/index.ts

@@ -0,0 +1,191 @@
+/**
+ * client-hmr, browser half: hot-reload driver for client plugin entries.
+ *
+ * Listens on the host's system SSE channel (`GET /plugins/events`); on a
+ * `rebuilt` frame it re-fetches the entry's bundle and swaps the cordis
+ * fiber in place. Every graph entry is a plugin bundle under the web2 model
+ * — `immediately` rows differ only in stage-one prefetch (a boot
+ * optimization), so all nine plugin packages share these reload semantics;
+ * normal packages (react family, cordis, shell, pure libs) are not entries
+ * and shell changes still mean a page reload. Cascade is zero-touch:
+ * downstream fibers key their activation epoch on provider fiber uids
+ * (vendor/cordis/src/fiber.ts `_refresh`), so replacing a provider fiber
+ * re-cascades natively — reloading a data-layer plugin (connection/runtime)
+ * cascades into its UI dependents with no HMR-side bookkeeping.
+ *
+ * Reload order (lazy CJS table): invalidate (drop the stale factory and
+ * materialized record) → prefetch (fetch + execute + register the fresh
+ * factory) → registry-first teardown → drain old fiber unload → remove
+ * owned `<style data-plugin>` tags → `entry.refresh()` materializes the new
+ * factory. Invalidate MUST precede prefetch: a live factory makes prefetch
+ * a no-op, and re-executing a bundle over an undeleted registration is a
+ * loud duplicate. The swap is safe because execution is pure registration
+ * under the lazy model — every module side effect (CSS injection included)
+ * lives in the factory closure and runs at materialization, inside
+ * refresh(). That also keeps the CSS ordering guarantee: owned styles are
+ * removed after the old fiber's disposers drained (SlotCore one-owner
+ * unregister) and before materialization re-injects tags under the same
+ * stable tag ids.
+ *
+ * Failure window: if prefetch rejects after invalidate, the module is left
+ * unregistered while the OLD fiber keeps running untouched (teardown never
+ * started) — degraded but recoverable, the next rebuilt frame retries from
+ * scratch. Consistent with the v1 no-rollback policy below. Known dev-only
+ * race: a rebuilt frame overlapping a still-in-flight boot arrival shares
+ * that arrival's task and may materialize the pre-rebuild bytes; the next
+ * rebuilt frame self-heals.
+ *
+ * Why not the naive `entry.fiber.dispose()` → `entry.refresh()` path —
+ * confirmed against vendor sources:
+ * 1. `Entry.fiber` is never cleared on dispose (vendor/loader/src/config/
+ *    entry.ts assigns it only in `_init`), so `refresh()` hits its
+ *    `if (this.fiber) return` guard and no-ops.
+ * 2. A bare `fiber.dispose()` lands in Loader's self-dispose branch
+ *    (vendor/loader/src/index.ts `internal/plugin` case 4: the registry
+ *    still holds the runtime at emit time), which flags the entry
+ *    `disabled: true` — permanently.
+ * vendor/hmr's reload skeleton documents the fix: delete the runtime record
+ * FIRST (`registry.delete` → case 4 returns early, the entry stays enabled),
+ * then rebuild. We additionally clear `entry.fiber` ourselves so
+ * `entry.refresh()` re-imports and re-plugins through the Loader's own
+ * `_init` (entry-resolved config, automatic `fiber.entry` rebinding) instead
+ * of hand-rolling `registry.plugin`. Client entries have exactly one fiber
+ * per runtime, so `registry.delete` never collaterally disposes siblings.
+ *
+ * Self-reload: this plugin is itself a graph entry, so a rebuilt frame may
+ * name it. The in-flight reload keeps running in the old bundle's closure
+ * (its EventSource closes with the old fiber's effects); the new bundle's
+ * apply opens a fresh channel. Frames arriving during the gap are lost —
+ * acceptable for the dev channel, the next rebuild renotifies.
+ *
+ * Failure policy (v1): no rollback. An import failure leaves the entry
+ * fiberless (the next rebuilt frame retries from scratch); an apply failure
+ * leaves a FAILED fiber for the shell's status projection. Both log loudly.
+ */
+import type { Context } from 'cordis'
+import type { Entry, Loader } from '@cordisjs/plugin-loader'
+import type { WebBootGraph } from '@deepseek-ai/dsh-client-modules'
+
+/**
+ * Frames on the `GET /plugins/events` system SSE channel (owned host-side by
+ * dsh-host-webserver's PluginEventFrame). Mirrored here because this is a
+ * wire boundary: frames arrive as JSON text and are validated at the parse
+ * point, not shared as a same-process typed seam.
+ */
+export type PluginsEventFrame =
+  | { type: 'graph'; graph: WebBootGraph }
+  | { type: 'rebuilt'; id: string; rev: string }
+
+/** System SSE endpoint pushing graph/rebuilt frames (wire protocol constant). */
+export const EVENTS_ENDPOINT = '/plugins/events'
+
+/** Cordis plugin name. */
+export const name = 'client-hmr'
+
+/** Required services: the vendored Loader (entry governance) and the client module system (boot provide, service name `modules`). */
+export const inject = ['loader', 'modules']
+
+/** Find the loader entry whose module specifier is `id` (entry tree ids are random; the package name lives in `options.name`). */
+function findEntry(loader: Loader, id: string): Entry | undefined {
+  for (const entry of loader.entries()) {
+    if (entry.options.name === id) return entry
+  }
+  return undefined
+}
+
+/** Remove every `<style data-plugin>` tag owned by `id` (attribute compared verbatim — no CSS-selector escaping pitfalls). */
+function removeOwnedStyles(id: string): void {
+  for (const el of document.querySelectorAll('style[data-plugin]')) {
+    if (el.getAttribute('data-plugin') === id) el.remove()
+  }
+}
+
+/**
+ * Mount the HMR driver: subscribe to the system SSE channel and hot-swap
+ * rebuilt entries.
+ * @param ctx - plugin context with `loader` and `modules` available.
+ */
+export function apply(ctx: Context): void {
+  // Both are declared injections (typed Context merges: `modules` from the
+  // client module loader package, `loader` from the vendored Loader).
+  const modLoader = ctx.modules
+  const loader: Loader = ctx.loader
+
+  async function reload(id: string): Promise<void> {
+    const entry = findEntry(loader, id)
+    if (entry === undefined) {
+      ctx.logger.warn(`client-hmr: rebuilt frame for unknown entry "${id}" (not in the loader tree)`)
+      return
+    }
+    // Invalidate first (drop stale factory + record — a live factory makes
+    // prefetch a no-op and re-registration a loud duplicate), then run the
+    // async half while the old fiber still serves: fetch + execute registers
+    // the fresh factory with zero side effects (lazy CJS — module bodies run
+    // at materialization, not execution).
+    modLoader.invalidate(id)
+    await modLoader.prefetch(id)
+
+    const oldFiber = entry.fiber
+    if (oldFiber !== undefined) {
+      // Registry-first teardown (see module comment): the runtime record must
+      // be gone before the fiber's disposer emits internal/plugin, or the
+      // Loader flags the entry disabled.
+      const runtime = oldFiber.runtime
+      if (runtime !== null) entry.ctx.registry.delete(runtime.callback)
+      // Drain the unload: effect disposers (slots, subscriptions) must finish
+      // before the new bundle executes and the new apply re-registers.
+      while (oldFiber.inertia !== undefined) await oldFiber.inertia
+      delete entry.fiber
+    }
+    // Old owned styles go before materialization re-injects them (the CSS
+    // idempotency guard keys on stable tag ids).
+    removeOwnedStyles(id)
+    // Re-init through the entry: fiber cleared above, so refresh() re-imports
+    // — materializing the prefetched factory (CSS injects here) — and
+    // re-plugins under the entry context. Import failures are logged by
+    // Entry._init and leave the entry fiberless (retryable).
+    await entry.refresh()
+    // Surface apply failures loudly (v1: no rollback, FAILED state stays).
+    await entry.fiber?.await()
+  }
+
+  // Serialize reloads: frames can arrive faster than a swap completes, and
+  // interleaved dispose/execute chains would corrupt the single-slot handoff.
+  let queue: Promise<void> = Promise.resolve()
+  const handle = (frame: PluginsEventFrame): void => {
+    switch (frame.type) {
+      case 'rebuilt':
+        queue = queue.then(() => reload(frame.id)).catch((error: unknown) => {
+          ctx.logger.error(`client-hmr: reload of "${frame.id}" failed`)
+          ctx.logger.error(error)
+        })
+        break
+      case 'graph':
+        // Connect-time snapshot, unused in v1. The loader's cached graph rev
+        // goes stale after rebuilds — harmless, since prefetch hits the
+        // network anyway (host serves bundles no-cache); graph rev refresh
+        // lands with the reconnect-handshake mechanism.
+        break
+      default:
+        // Merge-extensible frame union: unknown frame types from newer hosts
+        // are ignored by design.
+        break
+    }
+  }
+
+  ctx.effect(() => {
+    const source = new EventSource(EVENTS_ENDPOINT)
+    source.addEventListener('message', (event: MessageEvent<string>) => {
+      let frame: PluginsEventFrame
+      try {
+        frame = JSON.parse(event.data) as PluginsEventFrame
+      } catch {
+        // Wire boundary: a malformed dev-channel frame is dropped loudly.
+        ctx.logger.warn(`client-hmr: unparseable event frame: ${event.data}`)
+        return
+      }
+      handle(frame)
+    })
+    return () => { source.close() }
+  }, 'client-hmr: event source')
+}

packages/client/hmr/src/index.ts

@@ -0,0 +1,9 @@
+/**
+ * HMR plugin, node half. The package IS a dshClient plugin (dev-only row in
+ * the host graph): the reload driver lives in its client half in full
+ * (src/client/); the empty apply exists so the plugin appears in the host
+ * Loader (lifecycle governance + dshClient discovery).
+ */
+
+/** Host plugin body — no host-side behavior for the HMR plugin. */
+export function apply(): void {}

packages/client/hmr/src/invariant.ts

@@ -0,0 +1,33 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-client-hmr`.
+ * @module @deepseek-ai/dsh-client-hmr/invariant
+ */
+
+/* jscpd:ignore-start */
+import type { Context } from 'cordis'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-client-hmr'
+
+/** Cordis companion plugin name. */
+export const name = 'client-hmr-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/**
+ * No runtime invariant: a dev-only reload driver — it consumes the loader
+ * entry tree and module cache but owns no events and no cross-plugin mutable
+ * state; reload correctness (dispose → style removal → re-execute ordering)
+ * is observable only through the assembled browser runtime, not a host-side
+ * event relation.
+ */
+const install: InvariantInstaller = () => {}
+
+/**
+ * Register this package's invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))
+/* jscpd:ignore-end */