feat(M13): auto-PR via gh CLI after successful push (auto_pr=true)

New src/git/pr.ts helper wraps 'gh pr create'; returns { url } or { error }.
maybeCreateAutoPr() in update-job-status checks product.auto_pr, builds title
from story.code + task.title, writes pr_url to DB. Non-fatal: gh failure logs
a warning and leaves DONE status intact. Also syncs schema: auto_pr on Product,
pr_url on ClaudeJob.

__tests__/git/pr.test.ts

@@ -0,0 +1,69 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+
+const { mockExecFile } = vi.hoisted(() => ({ mockExecFile: vi.fn() }))
+
+vi.mock('node:child_process', () => ({ execFile: mockExecFile }))
+vi.mock('node:util', () => ({
+  promisify:
+    (fn: (...args: unknown[]) => void) =>
+    (...args: unknown[]) =>
+      new Promise((resolve, reject) =>
+        fn(...args, (err: Error | null, result: unknown) => (err ? reject(err) : resolve(result))),
+      ),
+}))
+
+import { createPullRequest } from '../../src/git/pr.js'
+
+beforeEach(() => {
+  vi.clearAllMocks()
+})
+
+describe('createPullRequest', () => {
+  it('returns PR URL when gh succeeds', async () => {
+    mockExecFile.mockImplementation(
+      (_cmd: string, _args: string[], _opts: unknown, cb: (err: null, res: { stdout: string; stderr: string }) => void) =>
+        cb(null, { stdout: 'Creating pull request...\nhttps://github.com/org/repo/pull/42\n', stderr: '' }),
+    )
+
+    const result = await createPullRequest({
+      worktreePath: '/worktrees/job-abc',
+      branchName: 'feat/job-abc',
+      title: 'SCRUM-1: Add feature',
+      body: 'Summary\n\n---\n\n*Auto-generated*',
+    })
+
+    expect(result).toEqual({ url: 'https://github.com/org/repo/pull/42' })
+  })
+
+  it('returns error when gh is not installed (ENOENT)', async () => {
+    mockExecFile.mockImplementation(
+      (_cmd: string, _args: string[], _opts: unknown, cb: (err: Error) => void) =>
+        cb(Object.assign(new Error('spawn gh ENOENT'), { code: 'ENOENT' })),
+    )
+
+    const result = await createPullRequest({
+      worktreePath: '/worktrees/job-abc',
+      branchName: 'feat/job-abc',
+      title: 'My PR',
+      body: 'Body',
+    })
+
+    expect(result).toMatchObject({ error: expect.stringContaining('gh CLI not found') })
+  })
+
+  it('returns error on generic gh failure', async () => {
+    mockExecFile.mockImplementation(
+      (_cmd: string, _args: string[], _opts: unknown, cb: (err: Error) => void) =>
+        cb(new Error('authentication required')),
+    )
+
+    const result = await createPullRequest({
+      worktreePath: '/worktrees/job-abc',
+      branchName: 'feat/job-abc',
+      title: 'My PR',
+      body: 'Body',
+    })
+
+    expect(result).toMatchObject({ error: expect.stringContaining('gh pr create failed') })
+  })
+})