fix: error-output sanitization + process-lifecycle hardening (#111) (#118)

Four findings from the 2026-05-31 audit (3×P2 + 1×P3), all in the error/process
lifecycle layer:

1. sanitizeError() helper — streaming error paths sent raw claude error_message /
   stderr to the client, leaking home-dir / credential-file paths that the
   non-streaming path already redacted. Factored the path-strip regex into one
   helper and applied it at all 9 client-facing jsonResponse/sendSSE error emits;
   de-duped the 3 pre-existing inline .replace() sites. Operator-log calls
   (logEvent/trackError) and admin-gated endpoints left raw by design.

2. res.on("close") SIGKILL escalation — a client disconnect sent only SIGTERM; a
   SIGTERM-resistant child held its concurrency slot until the request timeout
   (narrow #37 on the hottest exit path). Now escalates to SIGKILL 5s after SIGTERM,
   cleared on proc exit. Per review: gated on the child still being alive
   (exitCode===null && signalCode===null) so the normal-success close no longer
   fires a spurious SIGTERM or leaks the 5s timer; killTimer.unref() so a genuine
   disconnect timer never delays graceful shutdown.

3. Per-key quota TOCTOU — documented as best-effort/eventually-consistent (inline
   comment + README note): concurrent requests at the boundary can overshoot by up
   to MAX_CONCURRENT and cache hits are uncounted. Chose documentation over an
   in-flight counter to avoid a decrement-on-all-paths liability (the #37 class) on
   a low-blast-radius internal family rate-limiter — not a payment boundary.

4. [P3] overallTimer cleared on semantic completion — the request timer was cleared
   only on proc exit, so a streamed response that res.end()'d before the child
   exited could record a spurious post-success timeout. New clearOverallTimer()
   (clears the timer ONLY, never touches the `cleaned` slot-accounting flag — no
   slot leak) is called in the streaming stop-success path; cleanup() on exit still
   clears it idempotently and decrements the slot.

ALIGNMENT.md: error-shaping / process-lifecycle / rate-limit documentation forward
no Anthropic operation, so a cli.js citation is N/A under Rule 2. No blacklisted
tokens or port literals introduced; alignment.yml passes.

Independent fresh-context reviewer (opus): APPROVE WITH MINOR (Iron Rule 10) — the
two critical concerns (clearOverallTimer slot-leak class, SIGKILL double-kill) were
verified clean; MINOR #1 (kill-timer leak on success path) folded in; MINOR #2
(pre-existing regex over-redaction of ratios/URLs) left as out-of-scope.

Closes #111.

Co-authored-by: dtzp555 <dtzp555@gmail.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -486,6 +486,8 @@ When a key exceeds its quota, OCP returns HTTP 429 with a structured error:
 - Admin and anonymous users are never subject to quotas
 - PATCH is a partial update — omitted fields are left unchanged
 
+> **Note:** quotas are best-effort. Under concurrent bursts a key can exceed its cap by up to the server's max-concurrency (default 8), and cache hits are not counted toward quota. They cap budgets for cooperative family use, not adversarial abuse.
+
 ### Important Notes
 
 - All users share your Claude Pro/Max **rate limits** (5h session + 7d weekly)