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/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 */