chore(release): v3.21.1 — concurrency queue + spawn-token + TUI session-scope fixes (#151)

Patch release bundling three merged bug fixes (no new cli.js wire behavior,
no new endpoint/header/env var):

- #148 fix(tui): session prefix + reap/kill-server scoped per-instance by port
- #150 fix(server): serialize -p real-HOME token fallback behind a mutex +
  30s TTL keychain read cache + de-staled isolation decision (new lib/spawn-auth.mjs)
- #149 fix: semaphore honors runtime-lowered maxConcurrent, queued requests
  cancelled on client disconnect, singleflight follower retry on leader
  disconnect, exact queued accounting, quiet disconnect handling

Release-kit walk (CLAUDE.md Iron Rule 5.5): package.json version bump,
CHANGELOG.md entry, one-sentence Troubleshooting note for the genuinely
operator-visible upgrade-overlap caveat from #148. No changes to
models.json / Available Models / API Endpoints / Environment Variables
tables — verified by diffing all three merged commits (2922d68..d96da46);
none add an endpoint, header, or env var.

Co-authored-by: dtzp555 <dtzp555@gmail.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -894,6 +894,10 @@ node ~/ocp/scripts/sync-openclaw.mjs
 
 This is read-only at startup; the warning never blocks the gateway from running.
 
+### A TUI session vanished right after upgrading OCP
+
+If you ran a pre-3.21.1 OCP instance and a post-3.21.1 instance on the same host at the same time during an upgrade, the new instance's one-time boot reap can, once, kill an old-format (`ocp-tui-<8hex>`) live TUI session belonging to the still-running old instance — restart the affected session (`ocp restart` or re-run your TUI turn) and it will come back under the new instance's port-scoped naming.
+
 ### OpenClaw shows old models after `ocp update` (v3.10→v3.11 only)
 
 One-time bootstrap quirk for the v3.10.0 → v3.11.0 jump only — the running shell had the old `cmd_update` cached. Run once manually: