feat(example): sandbox-acp-agent — the live composition; RFCs to implemented

The three-entry cordis.yml (dsh-sandbox-local + dsh-bash-sandbox at a
read-only default + dsh-approval) served over ACP: the first live approval
composition. Recorded snapshot scenarios pin the wire end to end —
config-options advertisement, the mode-switching arc as the suite pinned
header (both switches, the prompt-section delta, one changed-by-the-user
notice per knob, a confined write landing under the switched mode), and
both escalation branches over scripted permissionAnswers (a grant runs
confined under workspace-write; a rejection executes nothing and pins the
fail-closed text). The with-key escalation e2e drives a real model +
real runner + the real bridge answerer, world-verified; ci.yml snapshot
lane and e2e.yml install bubblewrap so the confined replays actually
execute.

Both RFCs move to implemented/ (Decision/Consequences form, deferred
phases tracked in their own sections), with every cross-reference flipped.

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

@@ -9,7 +9,7 @@
  * `bwrap`, else the `landlock-run` Landlock launcher (kernel confinement
  * that needs no userns/mount privileges; distributed as the npm package
  * family `node-addon-landlock-run` — the decision recorded in
- * docs/rfc/proposed/feature/2026-07-06-sandbox.md); darwin: macOS
+ * docs/rfc/implemented/feature/2026-07-06-sandbox.md); darwin: macOS
  * `sandbox-exec` speaking a Seatbelt (SBPL) profile, unprobed.
  * When the platform has no chain or no candidate passes,
  * {@link LocalSandboxProvider.confine} FAILS CLOSED with the seam's