docs(bash): purge remaining trusted-plugin wording caught in review

Codex review of the reframe found stale "trusted-plugin surface/boundary"
wording still in review-relevant spots the first pass missed:

- docs/rfc/README.md index title for the RFC.
- packages/bash/bash-local/src/run.ts (childEnv JSDoc + SpawnSpec stdin/env
  JSDoc + the spawn stdin comment) and src/index.ts (resolve carry-through
  comment); run.ts also pointed at a tool-bash README section name that no
  longer exists.
- the two bash-local test descriptors (run.spec.ts / executor.spec.ts).
- the tool-bash guard test's `boundary-*` call ids and one "boundary
  assertion" comment (renamed to `no-forward-*`).

All reworded to the scrub-is-the-control framing (or neutral wording). The RFC
FILENAME keeps `-trusted-plugin-surface` as a stable id (many links point at it;
the index title and content are corrected). No code or behavior change.

docs/rfc/README.md

@@ -121,7 +121,7 @@ Do NOT write one for a mechanical or local choice (a variable name, a one-file r
 | [Branded IDs everywhere they belong](implemented/architecture/2026-06-20-branded-ids.md) | 2026-06-20 |
 | [Extract example apps into packages](implemented/architecture/2026-06-20-extract-example-app-packages.md) | 2026-06-20 |
 | [Event-domain semantics — session is the fact log, agent is the live surface](implemented/architecture/2026-06-30-event-domain-semantics.md) | 2026-06-30 |
-| [stdin + extra env on the bash seam — a trusted-plugin surface](implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md) | 2026-06-30 |
+| [stdin + extra env on the bash seam](implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md) | 2026-06-30 |
 
 ### Process