fix(review): contain provider-removed listener failures; pin the model-via-request path

ds-review-bot round 2, both warnings:

- subagent/provider-removed now routes through emitLifecycle (per-listener
  containment, the subagent/start|end precedent) instead of raw ctx.emit,
  whose dispatch halts on the first throw: a throwing subscriber can no
  longer starve a later mirror into keeping a stale tool, nor disrupt the
  backend fiber's teardown mid-disposer. provider-added deliberately keeps
  propagation (register-time rollback semantics, like the system-prompt
  registries); the asymmetry is documented on emitLifecycle, the event
  JSDoc, and the provider-lifecycle RFC.

- The documented model-via-agent/request fallback composes with a
  {{model}} persona via the ownership rule itself: the plugin supplying
  the model late states it early on the system-prompt/assemble waterfall.
  Declined re-ordering render after agent/request — it would break the
  agent/pre-step contract (compaction must measure the prompt the model
  sees). New loop test pins the supply path end-to-end; the RFC's
  {{model}} consequence bullet now covers supply as well as switch.

docs/cordis-catalog/services.md

@@ -176,7 +176,7 @@ list(): string[]
 start(name: string, request: SubagentStartRequest): SubagentRun
 ```
 
-Source: [`packages/subagent/subagent/src/index.ts:142`](../../packages/subagent/subagent/src/index.ts)
+Source: [`packages/subagent/subagent/src/index.ts:144`](../../packages/subagent/subagent/src/index.ts)
 
 ## `ctx.systemPrompt` — `SystemPrompt`