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/session-runner.ts

@@ -0,0 +1,60 @@
+import { query } from '@anthropic-ai/claude-agent-sdk';
+import { createAutoResponder } from './auto-responder.js';
+import type { BotConfig, StepName } from './types.js';
+
+export interface SessionOptions {
+  prompt: string;
+  config: BotConfig;
+  step: StepName;
+  maxTurns?: number;
+}
+
+export interface SessionResult {
+  sessionId: string | null;
+  output: string;
+  success: boolean;
+  duration: number;
+}
+
+export async function runSession(options: SessionOptions): Promise<SessionResult> {
+  const { prompt, config, step, maxTurns = 50 } = options;
+  const startTime = Date.now();
+  let output = '';
+  let sessionId: string | null = null;
+
+  try {
+    const session = query({
+      prompt,
+      options: {
+        cwd: config.projectDir,
+        maxTurns,
+        permissionMode: 'bypassPermissions',
+        allowDangerouslySkipPermissions: true,
+        canUseTool: createAutoResponder(config, step),
+        systemPrompt: { type: 'preset', preset: 'claude_code' },
+        settingSources: ['user', 'project'],
+      },
+    });
+
+    for await (const message of session) {
+      if (message.type === 'assistant') {
+        sessionId = message.session_id ?? sessionId;
+        for (const block of message.message.content) {
+          if (block.type === 'text') {
+            output += block.text + '\n';
+          }
+        }
+      } else if (message.type === 'result') {
+        sessionId = message.session_id ?? sessionId;
+      }
+    }
+
+    const duration = Date.now() - startTime;
+    const hasOutput = output.trim().length > 0;
+    return { sessionId, output, success: hasOutput, duration };
+  } catch (error) {
+    const duration = Date.now() - startTime;
+    const errorMsg = error instanceof Error ? error.message : String(error);
+    return { sessionId, output, success: false, duration };
+  }
+}