feat: session lifecycle audit log — append-only JSONL at ~/.claudeman/session-lifecycle.jsonl

Records every session create, start, exit, delete, recover, stale-clean,
mux-died, and server start/stop with timestamps, names, reasons, and exit
codes. Survives server restarts (unlike in-memory RunSummary).

- New SessionLifecycleLog singleton (src/session-lifecycle-log.ts)
- LifecycleEventType + LifecycleEntry types in types.ts
- GET /api/session-lifecycle endpoint with sessionId/event/since/limit filters
- cleanupSession() now takes reason parameter for audit trail
- state-store cleanupStaleSessions returns cleaned session IDs+names
- UI: lifecycle log modal accessible from header clipboard icon
- Auto-trims to 8k entries when exceeding 10k on server start

chore: bump version to 0.1556

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/types.ts

@@ -76,6 +76,32 @@ export type PlanTaskStatus = 'pending' | 'in_progress' | 'completed' | 'failed'
 /** TDD phase categories */
 export type TddPhase = 'setup' | 'test' | 'impl' | 'verify' | 'review';
 
+// ========== Session Lifecycle Audit Types ==========
+
+/** Types of session lifecycle events recorded to the audit log */
+export type LifecycleEventType =
+  | 'created'           // Session object created
+  | 'started'           // PTY process launched (interactive/shell/prompt)
+  | 'exit'              // PTY process exited (with exit code)
+  | 'deleted'           // cleanupSession() called — session removed
+  | 'recovered'         // Session restored from tmux on server restart
+  | 'stale_cleaned'     // Removed from state.json by cleanupStaleSessions()
+  | 'mux_died'          // tmux session died (detected by reconciliation)
+  | 'server_started'    // Server started (marker for restart detection)
+  | 'server_stopped';   // Server shutting down
+
+/** A single entry in the session lifecycle audit log */
+export interface LifecycleEntry {
+  ts: number;
+  event: LifecycleEventType;
+  sessionId: string;
+  name?: string;
+  mode?: string;
+  reason?: string;
+  exitCode?: number | null;
+  extra?: Record<string, unknown>;
+}
+
 // ========== Session Types ==========
 
 /**