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>

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## v3.21.1 — 2026-07-07
+
+Patch release: three bug fixes from an independent concurrency/session-lifecycle audit, each its own PR with a fresh-context reviewer (Iron Rule 10). No new `cli.js` wire behavior, no new endpoint, header, or env var; the `/health` field set is unchanged (only value truthfulness improved).
+
+### Fixed
+
+- **TUI session-scope / boot-reap (#148)** — `lib/tui/session.mjs`'s tmux session prefix is now scoped per-instance by listen port (`ocp-tui-<port>-`) instead of a bare host-wide `ocp-tui-` constant, so a second OCP instance on the same host (e.g. a temporary verification instance) can no longer have its live TUI sessions reaped or `kill-server`'d by another instance's boot/periodic sweep. The one-time boot reap also claims exact-shape legacy `ocp-tui-<8hex>` sessions (pre-fix naming) once, to clean up zombies left behind across an in-place upgrade.
+- **`-p` spawn-token mutex + keychain caching (#150)** — the real-HOME token fallback used when the keychain token is within its 5-minute expiry window is now serialized behind a mutex, so concurrent `-p` spawns no longer race the same single-use refresh token against each other (the credential-fork hazard). Added a 30s TTL cache + last-good-label memoization for the keychain read, cutting per-spawn event-loop blocking. The isolation decision (`/health` isolated/real-home reporting) is now re-evaluated per spawn instead of memoized forever, so `/health` no longer misreports a stale decision. New module `lib/spawn-auth.mjs` extracts the pure, unit-testable primitives (mutex, TTL cache, expiry gate, label ordering).
+- **Concurrency queue / disconnect handling (#149)** — the shared semaphore now honors a runtime-lowered `maxConcurrent` immediately (previously a decrease was silently ignored until in-flight tasks finished on their own) and wakes queued waiters right away when the limit is raised. Queued `-p`/TUI requests are now linked to the client's HTTP connection via `AbortSignal`; a client that disconnects while queued is spliced out of the queue instead of still spawning `claude` once a slot frees. A singleflight follower whose leader disconnected now retries instead of inheriting a spurious 500, and a queued-then-disconnected request is no longer recorded as a usage failure or logged as an error (quiet disconnect handling).
+
 ## v3.21.0 — 2026-06-25
 
 Cleanup + docs release: TUI dead-code removal, docs honesty, and release prep. No new `cli.js` wire behavior; the default path (`CLAUDE_TUI_MODE` unset) is byte-for-byte unchanged.