feat: add plan2code-bot with --resume capability and state cleanup

Add the autonomous workflow test runner (plan2code-bot) that uses the
Claude Agent SDK to run plan2code end-to-end. Includes --resume flag
to continue incomplete runs from saved state, and automatic state file
cleanup on successful completion.

plan2code-bot/src/bot-state.ts

@@ -0,0 +1,48 @@
+import fs from 'fs-extra';
+import path from 'path';
+import type { BotState } from './types.js';
+
+const STATE_FILE = '.plan2code-bot-state.json';
+
+export function saveState(state: BotState): void {
+  const filePath = path.join(state.config.projectDir, STATE_FILE);
+  fs.writeJsonSync(filePath, state, { spaces: 2 });
+}
+
+export function loadState(projectDir: string): BotState | null {
+  const filePath = path.join(projectDir, STATE_FILE);
+  if (!fs.existsSync(filePath)) {
+    return null;
+  }
+  return fs.readJsonSync(filePath) as BotState;
+}
+
+export function deleteState(projectDir: string): void {
+  const filePath = path.join(projectDir, STATE_FILE);
+  if (fs.existsSync(filePath)) {
+    fs.removeSync(filePath);
+  }
+}
+
+/**
+ * Search for an existing state file in workDir (enhancement mode)
+ * or in immediate subdirectories (new-project mode).
+ */
+export function findExistingState(workDir: string): BotState | null {
+  // Enhancement mode: state is in workDir directly
+  const direct = loadState(workDir);
+  if (direct) return direct;
+
+  // New-project mode: state is in a subdirectory
+  try {
+    for (const entry of fs.readdirSync(workDir, { withFileTypes: true })) {
+      if (entry.isDirectory()) {
+        const sub = loadState(path.join(workDir, entry.name));
+        if (sub) return sub;
+      }
+    }
+  } catch {
+    // workDir not readable — ignore
+  }
+  return null;
+}