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/bash/bash-sandbox/src/index.ts

@@ -31,7 +31,7 @@
  *
  * Deny-only at the seam, escalation at the tool: a denial is a reported FACT
  * here, and the one-shot user-approved escalated retry of a denied action
- * (docs/rfc/proposed/feature/2026-07-06-sandbox.md) is driven by
+ * (docs/rfc/implemented/feature/2026-07-06-sandbox.md) is driven by
  * `dsh-tool-bash` through `ctx.approval` — this executor's contribution is the
  * per-call `sandboxMode` override it honors in {@link resolve}: an escalated
  * call runs (and classifies, and reports) under ITS granted mode while every