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/README.md

@@ -7,6 +7,6 @@ The confinement half of the [capability-seam split](../../docs/rfc/implemented/a
 | `sandbox/` | Abstract process-sandbox seam (the `SandboxProvider` contract + the mode/enforcement/policy vocabulary) | `ctx.sandbox` |
 | `sandbox-local/` | Local backends by platform chain: Linux `bwrap` else the `landlock-run` launcher (the npm-distributed [`node-addon-landlock-run`](https://www.npmjs.com/package/node-addon-landlock-run) family, built and released from its own repository), darwin `sandbox-exec`/Seatbelt — multi-candidate chains functionally probed, sole candidates selected directly, verdict cached, fail-closed | (registers `ctx.sandbox`) |
 
-The seam confines SAME-WORLD subprocesses only (shared filesystem and kernel). Containers, microVMs, and remote executors are NOT backends here — they replace whole capability implementations (`ctx.bash`, `ctx.fs`) as environment-coherent groups; the boundary is recorded in [the sandbox RFC](../../docs/rfc/proposed/feature/2026-07-06-sandbox.md).
+The seam confines SAME-WORLD subprocesses only (shared filesystem and kernel). Containers, microVMs, and remote executors are NOT backends here — they replace whole capability implementations (`ctx.bash`, `ctx.fs`) as environment-coherent groups; the boundary is recorded in [the sandbox RFC](../../docs/rfc/implemented/feature/2026-07-06-sandbox.md).
 
-The staged first consumer is the sandboxed bash executor (it hands over the exact `['bash', '-c', command]` argv it is about to spawn). In-process tools (fs/web) cannot be confined by an OS wrapper — their sandbox semantics are policy at their own seams (the sandbox RFC's cross-family phase).
+Consumers today: [`bash/bash-sandbox`](../bash/bash-sandbox/) (wraps `['bash', '-c', command]`; see [examples/sandbox-acp-agent](../../examples/sandbox-acp-agent/) for the composed leaf). In-process tools (fs/web) cannot be confined by an OS wrapper — their sandbox semantics are policy at their own seams (the sandbox RFC's cross-family phase).