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/README.md

@@ -1,6 +1,6 @@
 # @deepseek-ai/dsh-sandbox-local
 
-Local implementation of the [`@deepseek-ai/dsh-sandbox`](../sandbox/) seam: wraps a caller's argv in a platform confinement runner. Selection is BY PLATFORM, resolved once and cached: each platform names its runner chain, a chain of one is selected directly (probing arbitrates between candidates — a sole candidate leaves nothing to arbitrate), and a chain of several is probed functionally in preference order. Linux: [`bwrap`](https://github.com/containers/bubblewrap) when its probe passes, else the [`landlock-run`](https://www.npmjs.com/package/node-addon-landlock-run) Landlock launcher (kernel confinement that needs no userns/mount privileges — see the [sandbox RFC](../../../docs/rfc/proposed/feature/2026-07-06-sandbox.md) for the prebuilt-binary decision and profile-parity notes); darwin: `sandbox-exec` speaking a Seatbelt (SBPL) profile, unprobed. A platform with no chain means `confine()` FAILS CLOSED with the seam's structured `SANDBOX_UNAVAILABLE` error (win32 today: a reserved, deliberately empty chain awaiting an AppContainer-family runner); an unprobed runner that turns out unusable fails closed at EXECUTION instead — it refuses to run the command, and every wrap's `runnerFailureSignatures` let the consumer classify that as a sandbox failure rather than a task failure. Never a silent unconfined passthrough on any path.
+Local implementation of the [`@deepseek-ai/dsh-sandbox`](../sandbox/) seam: wraps a caller's argv in a platform confinement runner. Selection is BY PLATFORM, resolved once and cached: each platform names its runner chain, a chain of one is selected directly (probing arbitrates between candidates — a sole candidate leaves nothing to arbitrate), and a chain of several is probed functionally in preference order. Linux: [`bwrap`](https://github.com/containers/bubblewrap) when its probe passes, else the [`landlock-run`](https://www.npmjs.com/package/node-addon-landlock-run) Landlock launcher (kernel confinement that needs no userns/mount privileges — see the [sandbox RFC](../../../docs/rfc/implemented/feature/2026-07-06-sandbox.md) for the prebuilt-binary decision and profile-parity notes); darwin: `sandbox-exec` speaking a Seatbelt (SBPL) profile, unprobed. A platform with no chain means `confine()` FAILS CLOSED with the seam's structured `SANDBOX_UNAVAILABLE` error (win32 today: a reserved, deliberately empty chain awaiting an AppContainer-family runner); an unprobed runner that turns out unusable fails closed at EXECUTION instead — it refuses to run the command, and every wrap's `runnerFailureSignatures` let the consumer classify that as a sandbox failure rather than a task failure. Never a silent unconfined passthrough on any path.
 
 Policy is per call (`SandboxPolicy`: mode + workspace root); the provider holds only the mechanism and the cached ladder verdict. Every wrap reports the selected runner's `enforcement` (`full`, or `partial` on an older Landlock ABI that governs only a subset of accesses — read from the launcher's `--probe` report line) and its `denialSignatures` — the stderr dialect that rung's kernel speaks on a denied file effect (EROFS text under bwrap, EACCES under Landlock, EPERM under Seatbelt), which stderr-inferring consumers match instead of a cross-runner union. A non-empty `runnerCommand` config is the operator's assertion of a runner that fully enforces the bwrap-shaped profile: the ladder and probes are skipped (the wrap carries both Linux denial dialects, the mechanism being unknown) — also the deterministic fake-runner seam for keyless test tiers. Its runner-failure dialect is the OUTER shell's argv0-scoped failure shapes (`exec: <argv0>: not found`, `<argv0>: No such file or directory`, `<argv0>: Permission denied`) — the consumer re-joins the wrap through `bash -c 'exec …'`, so a missing or unexecutable configured runner classifies as a sandbox failure (fail closed at execution), never as a failing command or a denial. `probeTimeoutMs` (default 5000) bounds each functional probe, the escape hatch for hosts slow enough that a timed-out probe would otherwise misread as `SANDBOX_UNAVAILABLE`.
 
@@ -15,4 +15,4 @@ Every rung has its keyless world-proof (`tests/bwrap.e2e.ts`, `tests/landlock.e2
   name: '@deepseek-ai/dsh-sandbox-local'
 ```
 
-The staged first consumer is the sandboxed bash executor.
+Consumers: [`@deepseek-ai/dsh-bash-sandbox`](../../bash/bash-sandbox/); see [`examples/sandbox-acp-agent`](../../../examples/sandbox-acp-agent/) for the runnable composition.

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