fix(review): harden cron security, session lifecycle, skip policy (PR #141)

- Reject multi-line prompts end-to-end: schema refines on promptText/
  launchCommand, runtime check in resolvePrompt (prompt-file content;
  trailing newlines tolerated), matching cron-ui form validation — delivery
  is single-line only, so multi-line was silently corrupted (typed mode
  fused lines, paste mode submitted partials)
- Close the workingDir confinement bypass (arbitrary server-side file read,
  e.g. workingDir=/proc + /proc/self/environ): realpath-resolve workingDir
  before the containment check, reject '/' and blocked/pseudo-fs trees
  (/proc, /sys, /dev + the attachment-guard blocklist) at fire time AND at
  job create/update (workingDir must exist and be a directory)
- Session lifecycle: new per-job autoClosePreviousSession (default true,
  recurring schedules only; ignored for 'once') — the previous run's
  still-open session is closed via the normal cleanupSession path when the
  next run fires; UI switch added; 50-session cap math documented in
  docs/cron-guide.md §8
- skip_if_same_agent_running: count only live sessions (exclude
  stopped/error dead tabs), exclude sessions created by this job's own runs
  (fixes the fire-once-then-skip-forever self-deadlock), and a skipped
  'once' job stays armed and retries next tick instead of being consumed;
  liveness filter mirrored in cron-ui _countActiveAgents
- Wire launchCommand (was accepted+documented but dead): shell mode sends
  it via writeViaMux as the first input line after startShell readiness
  (single-line, schema-enforced); form field shown for shell agent type
- Record delivery failures: a false writeViaMux result now fails the run
  instead of recording a false 'prompt_sent'
- Cap saved jobs at MAX_CRON_JOBS (100) to bound state.json growth
- Surface field-specific schema messages (drop parseBody custom
  errorMessage on cron create/update)
- Tests: workingDir create/update validation, /proc bypass regression,
  single-line enforcement (schema+runtime+trailing-newline tolerance),
  live/own-session skip filtering, once-skip re-arm, auto-close on/off/once,
  job-count cap

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/types/cron.ts

@@ -63,6 +63,13 @@ export interface CronJob {
   notes?: string;
   /** Applies to automatic (scheduled) runs only. Manual Run Now always warns client-side. */
   concurrencyPolicy: ConcurrencyPolicy;
+  /**
+   * Close the still-open session created by this job's previous run before the
+   * next run launches (via the normal session-cleanup path), so unattended
+   * recurring jobs don't accumulate tabs until the global session cap.
+   * Default true. Ignored for 'once' schedules.
+   */
+  autoClosePreviousSession?: boolean;
 
   // ── Bookkeeping (server-maintained) ─────────────────────────────────────
   createdAt: number;