fix(claw): mount group folder and sessions into container

claw was running containers with no volume mounts, so the agent
always saw an empty /workspace/group. Add build_mounts() to
replicate the same bind-mounts that container-runner.ts sets up
(group folder, .claude sessions, IPC dir, agent-runner source,
and project root for main).

Also includes upstream fix from qwibitai/nanoclaw#1368:
graceful terminate() before kill() on output sentinel, and early
return after a successful structured response so exit code stays 0.

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

src/claw-skill.test.ts

@@ -0,0 +1,45 @@
+import fs from 'fs';
+import os from 'os';
+import path from 'path';
+import { spawnSync } from 'child_process';
+
+import { describe, expect, it } from 'vitest';
+
+describe('claw skill script', () => {
+  it('exits zero after successful structured output even if the runtime is terminated', () => {
+    const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'claw-skill-test-'));
+    const binDir = path.join(tempDir, 'bin');
+    fs.mkdirSync(binDir, { recursive: true });
+
+    const runtimePath = path.join(binDir, 'container');
+    fs.writeFileSync(
+      runtimePath,
+      `#!/bin/sh
+cat >/dev/null
+printf '%s\n' '---NANOCLAW_OUTPUT_START---' '{"status":"success","result":"4","newSessionId":"sess-1"}' '---NANOCLAW_OUTPUT_END---'
+sleep 30
+`,
+    );
+    fs.chmodSync(runtimePath, 0o755);
+
+    const result = spawnSync(
+      'python3',
+      ['.claude/skills/claw/scripts/claw', '-j', 'tg:123', 'What is 2+2?'],
+      {
+        cwd: process.cwd(),
+        encoding: 'utf8',
+        env: {
+          ...process.env,
+          NANOCLAW_DIR: tempDir,
+          PATH: `${binDir}:${process.env.PATH || ''}`,
+        },
+        timeout: 15000,
+      },
+    );
+
+    expect(result.status).toBe(0);
+    expect(result.signal).toBeNull();
+    expect(result.stdout).toContain('4');
+    expect(result.stderr).toContain('[session: sess-1]');
+  });
+});