refactor: split types.ts into domain modules (phase 4, step 1)

Split 1,443-line types.ts into 14 focused domain files under src/types/:
common.ts, session.ts, task.ts, app-state.ts, respawn.ts, ralph.ts,
api.ts, lifecycle.ts, run-summary.ts, tools.ts, teams.ts, push.ts,
plan.ts, and index.ts barrel.

Moved PlanItem interface from plan-orchestrator.ts into types/plan.ts
to break circular dependency. Original types.ts replaced with barrel
re-export — zero changes to 36 import sites.

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

src/types/lifecycle.ts

@@ -0,0 +1,28 @@
+/**
+ * @fileoverview 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
+  | 'detached' // Server shutdown — PTY left alive in tmux for recovery
+  | '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>;
+}