feat(web): add session model selector

.agents/notes/implemented/architecture/2026-07-23-client-plugin-loading-model.md

@@ -27,7 +27,7 @@ The first-generation client loader (`createClientLoader`) hand-wrote both layers
 What makes a package a plugin? One rule: **a package is a plugin package once its consumption is cordis dependency injection; until then it is a plain package.** How code reaches the page is not part of the taxonomy — arrival follows from the kind instead of defining it.
 
 - **Plain packages** are the absolute base the module system itself needs, plus libraries not yet converted to DI: the react family, cordis, `@deepseek-ai/dsh-client-modules` (the module system itself — it can never be a plugin, because modules precede all modules), the web shell kernel, and — for now — ui-slots, web-react, ui-primitives. Plain packages are shell-bundled, seeded into the module table, and invisible to the host graph.
-- **Plugin packages** are everything else. Each one carries a `dshClient` manifest declaration (`{ platform, inject, immediately? }`) and one uniform shape: the shared tsdown preset emits `lib/client.js`, and `exports["./client"]` points at that bundle. Each is a governed entry of the host-authored graph. Nine exist today: connection, runtime, ui-theme, i18n, hmr (dev graphs only), ui-layout, ui-sidebar, ui-conversation, ui-trajectory.
+- **Plugin packages** are everything else. Each one carries a `dshClient` manifest declaration (`{ platform, inject, immediately? }`) and one uniform shape: the shared tsdown preset emits `lib/client.js`, and `exports["./client"]` points at that bundle. Each is a governed entry of the host-authored graph. The current set is connection, runtime, ui-theme, i18n, hmr (dev graphs only), ui-layout, ui-sidebar, ui-conversation, ui-model-selector, ui-question, and ui-trajectory.
 
 The manifest owns the package's loading contract: its `inject` dependency edges, plus the optional `immediately` prefetch mark (absent means lazy). The composing app owns only the roster and the `--dev` switch.
 
@@ -39,7 +39,7 @@ Four edge rules govern imports across the two kinds. None of them depends on any
 
 - **Plugin ↔ plugin value imports are a build error.** This holds regardless of either side's `immediately` declaration — the rule must not depend on a mark someone can flip. Cooperation goes through cordis inject/services. `import type` is exempt; the type chain is untouched. This rule is why `scopeOf` is a `SessionsService` method and why `transportError` lives in `dsh-host-apiproxy`'s wire layer (its `RpcResult` home, inline-safe).
 - **Plugin → plain package value imports are externals**, judged against the platform list. That list is one constant in the shell (`platform.ts`: react family, cordis, ui-slots, web-react, ui-primitives), imported by both the tsdown preset (for the external judgement) and `seed.ts` (for the table warm-up). One constant, two consumers — the hand-sync drift class stays dead.
-- **The purity gate covers all nine plugin packages.** Its three branches: platform imports become externals; INLINE_SAFE wire layers are inlined; any other workspace leak is a build error. The uniform bundle shape is what makes this coverage total — every plugin builds through the same preset, so no package can sit outside the gate.
+- **The purity gate covers every plugin package.** Its three branches: platform imports become externals; INLINE_SAFE wire layers are inlined; any other workspace leak is a build error. The uniform bundle shape is what makes this coverage total — every plugin builds through the same preset, so no package can sit outside the gate.
 - **The shell is self-sufficient.** The kernel (boot + loading page) value-imports no plugin package; its status stores are hand-rolled. The fail-loud presentation must not depend on the system whose failure it reports.
 
 ### One module system, one plugin governor
@@ -88,7 +88,7 @@ On the browser side, the driver reloads one plugin per frame, serialized:
 6. `entry.refresh()` — re-imports, materializing the fresh factory. CSS re-injects here, under the same stable tag ids.
 7. `fiber.await()` — rethrows loud.
 
-All nine plugins share this one semantics; an `immediately` row reloads exactly like a lazy one. Dependency cascade costs zero client code: a fiber's activation epoch strings its service providers' uids, so replacing a provider's fiber re-loads every dependent through cordis itself. Reloading connection or runtime cascades the whole UI — correct, if heavy.
+Every plugin shares this one semantics; an `immediately` row reloads exactly like a lazy one. Dependency cascade costs zero client code: a fiber's activation epoch strings its service providers' uids, so replacing a provider's fiber re-loads every dependent through cordis itself. Reloading connection or runtime cascades the whole UI — correct, if heavy.
 
 The support boundary, stated honestly. Reload is coarse by design: fresh fiber, fresh components, React state lost, data layer untouched — react-refresh-grade state preservation conflicts with "re-executing the bundle re-runs the factory" and is deliberately out. Plain packages (react family, shell kernel, not-yet-promoted libraries) are not entries: changing them means a shell rebuild and a full page reload. No rollback in v1: an import failure leaves the entry fiberless and the next rebuilt frame retries from scratch; an apply failure leaves a FAILED fiber for the status projection; both log loudly. Self-reload works — the in-flight reload finishes in the old bundle's closure and the new apply opens a fresh SSE channel — but frames arriving in the gap are lost, and the next rebuild renotifies. One 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 frame self-heals.