feat: add Run Summary feature for session activity tracking

Implements a "what happened while you were away" view for sessions:
- Track significant events: session start/stop, respawn cycles, state changes,
  idle/working transitions, token milestones, auto-compact/clear, Ralph
  completions, AI check results, hook events, errors/warnings
- Stats dashboard: respawn cycles, peak tokens, active/idle time, issue counts
- Timeline view with color-coded severity and emoji icons
- Filter events by type (all/errors/warnings/respawn/idle)
- State stuck detection (warns when state unchanged for 10+ minutes)

Click the chart icon on any session tab to open the Run Summary modal.

Files:
- src/run-summary.ts: RunSummaryTracker class with event tracking
- src/types.ts: RunSummary, RunSummaryEvent types
- src/web/server.ts: Integration with session/respawn events, API endpoint
- src/web/public/: Modal UI, timeline rendering, filter controls
- docs/run-summary-plan.md: Implementation plan

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/types.ts

@@ -859,6 +859,121 @@ export function getErrorMessage(error: unknown): string {
   return 'An unknown error occurred';
 }
 
+// ========== Run Summary Types ==========
+
+/**
+ * Types of events tracked in the run summary.
+ * These provide a historical view of what happened during a session.
+ */
+export type RunSummaryEventType =
+  | 'session_started'
+  | 'session_stopped'
+  | 'respawn_cycle_started'
+  | 'respawn_cycle_completed'
+  | 'respawn_state_change'
+  | 'error'
+  | 'warning'
+  | 'token_milestone'
+  | 'auto_compact'
+  | 'auto_clear'
+  | 'idle_detected'
+  | 'working_detected'
+  | 'ralph_completion'
+  | 'ai_check_result'
+  | 'hook_event'
+  | 'state_stuck';
+
+/**
+ * Severity levels for run summary events.
+ */
+export type RunSummaryEventSeverity = 'info' | 'warning' | 'error' | 'success';
+
+/**
+ * A single event in the run summary timeline.
+ */
+export interface RunSummaryEvent {
+  /** Unique event identifier */
+  id: string;
+  /** Timestamp when event occurred */
+  timestamp: number;
+  /** Type of event */
+  type: RunSummaryEventType;
+  /** Severity level for display */
+  severity: RunSummaryEventSeverity;
+  /** Short title for the event */
+  title: string;
+  /** Optional detailed description */
+  details?: string;
+  /** Optional additional metadata */
+  metadata?: Record<string, unknown>;
+}
+
+/**
+ * Statistics aggregated from run summary events.
+ */
+export interface RunSummaryStats {
+  /** Number of respawn cycles completed */
+  totalRespawnCycles: number;
+  /** Total tokens used during this run */
+  totalTokensUsed: number;
+  /** Peak token count observed */
+  peakTokens: number;
+  /** Total time Claude was actively working (ms) */
+  totalTimeActiveMs: number;
+  /** Total time Claude was idle (ms) */
+  totalTimeIdleMs: number;
+  /** Number of errors encountered */
+  errorCount: number;
+  /** Number of warnings encountered */
+  warningCount: number;
+  /** Number of AI idle checks performed */
+  aiCheckCount: number;
+  /** Timestamp when last became idle */
+  lastIdleAt: number | null;
+  /** Timestamp when last started working */
+  lastWorkingAt: number | null;
+  /** Total number of state transitions */
+  stateTransitions: number;
+}
+
+/**
+ * Complete run summary for a session.
+ * Provides a historical view of session activity for users returning after absence.
+ */
+export interface RunSummary {
+  /** Session ID this summary belongs to */
+  sessionId: string;
+  /** Session display name */
+  sessionName: string;
+  /** Timestamp when tracking started */
+  startedAt: number;
+  /** Timestamp of last update */
+  lastUpdatedAt: number;
+  /** Timeline of events (most recent last) */
+  events: RunSummaryEvent[];
+  /** Aggregated statistics */
+  stats: RunSummaryStats;
+}
+
+/**
+ * Creates initial run summary stats.
+ */
+export function createInitialRunSummaryStats(): RunSummaryStats {
+  return {
+    totalRespawnCycles: 0,
+    totalTokensUsed: 0,
+    peakTokens: 0,
+    totalTimeActiveMs: 0,
+    totalTimeIdleMs: 0,
+    errorCount: 0,
+    warningCount: 0,
+    aiCheckCount: 0,
+    lastIdleAt: null,
+    lastWorkingAt: null,
+    stateTransitions: 0,
+  };
+}
+
 // ========== Spawn1337 Protocol Re-exports ==========
 
 export type {