fix(docs): address Codex review — document the subagent_fork alias, harden dispose

Round-1 Codex review findings on the tool-schema catalog:

(A) The shipped coding-agent / acp-agent configs load dsh-tool-subagent twice —
as `subagent` (spawn backend) and `subagent_fork` (fork backend) — so the model
sees a `subagent_fork` tool the catalog never mentioned, while the intro claimed
to list "the exact name the model receives". The registered name is the plugin's
load-time `toolName` config, not a package fact, so rather than bake an
example-app config into a packages-scoped generator, add a per-package deployment
`note`: the subagent entry now records the `subagent_fork` alias and points at the
leaf configs. Intro and RFC scope reworded to state the unit is the package (at
its default config), with aliases noted — no longer overclaiming. A test asserts
the note names `subagent_fork`, covering the config-driven-name path.

(B) collectToolCatalog only disposed the context on the success path; a throw from
mount/schemas() after earlier plugins mounted would leak the fiber. Move
`ctx.fiber.dispose()` into a `finally` per the repo's dispose-to-quiescence rule.

packages/core/tools/tests/gen-tool-catalog.spec.ts

@@ -60,6 +60,18 @@ describe('gen-tool-catalog collectToolCatalog', () => {
     const bash = catalog.find(entry => entry.pkg === '@deepseek-ai/dsh-tool-bash')
     expect(bash?.source).toBe('packages/bash/tool-bash/src/index.ts')
   })
+
+  it('records the shipped `subagent_fork` alias in a note (config-driven tool name)', async () => {
+    // `tool-subagent`'s registered name is the load-time `toolName` config, so
+    // the shipped agents surface this one package as both `subagent` and
+    // `subagent_fork`. Booting yields only the default name; the note is how a
+    // reader learns the fork alias the model also sees. Without it the catalog
+    // would silently under-report the shipped tool surface.
+    const catalog = await collectToolCatalog()
+    const subagent = catalog.find(entry => entry.pkg === '@deepseek-ai/dsh-tool-subagent')
+    expect(subagent?.schemas.map(s => s.name)).toEqual(['subagent'])
+    expect(subagent?.note).toMatch(/subagent_fork/)
+  })
 })
 
 describe('gen-tool-catalog assertManifestComplete', () => {