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.

packages/bash/bash-local/src/index.ts

@@ -116,8 +116,8 @@ export class LocalBashExecutor extends BashExecutor {
       workdir: request.workdir ?? this.config.cwd ?? process.cwd(),
       timeoutMs,
       ...request.signal ? { signal: request.signal } : {},
-      // Carry the trusted-plugin stdin/env through verbatim — optional, no
-      // config default (absent means none). env merges AFTER the scrub in run.ts.
+      // Carry stdin/env through verbatim — optional, no config default (absent
+      // means none). env merges AFTER the scrub in run.ts.
       ...request.stdin !== undefined ? { stdin: request.stdin } : {},
       ...request.env !== undefined ? { env: request.env } : {},
       // Carry the owner through verbatim (required-but-nullable on the spec):