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/plan.ts

@@ -0,0 +1,65 @@
+/**
+ * @fileoverview Plan orchestrator type definitions
+ */
+
+/** Task execution status for plan tracking */
+export type PlanTaskStatus = 'pending' | 'in_progress' | 'completed' | 'failed' | 'blocked';
+
+/** TDD phase categories */
+export type TddPhase = 'setup' | 'test' | 'impl' | 'verify' | 'review';
+
+/** Development phase in TDD cycle (alias for TddPhase) */
+export type PlanPhase = TddPhase;
+
+/**
+ * Configuration for process priority using `nice`.
+ * Lower priority reduces CPU contention with other processes.
+ */
+export interface NiceConfig {
+  /** Whether nice priority is enabled */
+  enabled: boolean;
+  /** Nice value (-20 to 19, default: 10 = lower priority) */
+  niceValue: number;
+}
+
+export const DEFAULT_NICE_CONFIG: NiceConfig = {
+  enabled: false,
+  niceValue: 10,
+};
+
+/**
+ * Process resource statistics
+ */
+export interface ProcessStats {
+  /** Memory usage in megabytes */
+  memoryMB: number;
+  /** CPU usage percentage */
+  cpuPercent: number;
+  /** Number of child processes */
+  childCount: number;
+  /** Timestamp of stats collection */
+  updatedAt: number;
+}
+
+/**
+ * A single plan item for plan orchestration.
+ * Moved here from plan-orchestrator.ts to break circular dependency.
+ */
+export interface PlanItem {
+  id?: string;
+  content: string;
+  priority: 'P0' | 'P1' | 'P2' | null;
+  source?: string;
+  rationale?: string;
+  verificationCriteria?: string;
+  testCommand?: string;
+  dependencies?: string[];
+  status?: PlanTaskStatus;
+  attempts?: number;
+  lastError?: string;
+  completedAt?: number;
+  complexity?: 'low' | 'medium' | 'high';
+  tddPhase?: PlanPhase;
+  pairedWith?: string;
+  reviewChecklist?: string[];
+}