feat: branch-per-story + worktree-defer + verify EMPTY edge-cases (#12)

Implementeert vier open stories uit PBI 'Veilige Claude-agent-workflow':

**Branch per story (cmon11tbe001zbortx35n155c)**
- `resolveBranchForJob`: zoek sibling-job in dezelfde story; reuse z'n
  branch (1 PR per story i.p.v. per task).
- Branch-naam: `feat/story-<8-char>` voor nieuwe stories.
- `createWorktreeForJob` kent nu `reuseBranch=true`: detecteert stale
  sibling-worktree die de branch nog vasthoudt en verwijdert die eerst.
- `attachWorktreeToJob` neemt `storyId` mee.

**PR-hergebruik (zelfde story)**
- `maybeCreateAutoPr`: als sibling-job in story al een pr_url heeft,
  hergebruik die zonder nieuwe `gh pr create`-call. PR-titel komt nu
  van de story (was task) zodat het als 'story-PR' leest.

**Worktree-cleanup uitgesteld bij actieve siblings**
- `cleanupWorktreeForTerminalStatus`: count active sibling-jobs in
  dezelfde story; defer als > 0 (volgende sub-task gebruikt branch).

**Worktree-cleanup logging (cmon0jc14001ubortjxf2a2ck)**
- Warning bij ontbrekende repoRoot, met productId + jobId in message.
- Warning bij removeWorktreeForJob-failure met keepBranch in message.

**resolveRepoRoot fallback (cmon0jc14001ubortjxf2a2ck)**
- Convention-based fallback: `~/Projects/<repo-name>` afgeleid uit
  `product.repo_url` als noch env-var noch config-bestand iets oplevert.
- `repoNameFromUrl` helper geëxporteerd voor herbruikbaarheid.

**Verify EMPTY-detection edge-case (cmon0kdq6001xbort2kgbcqmr)**
- `classifyDiffAgainstPlan`: na file-paths-check ook content-lines
  checken; als alle +/- regels alleen headers of whitespace zijn,
  return EMPTY met duidelijke reasoning.

Tests: 120/120 groen (3 nieuwe), tsc clean, build clean.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/tools/update-job-status.ts

@@ -30,14 +30,45 @@ export async function cleanupWorktreeForTerminalStatus(
   branch: string | undefined,
 ): Promise<void> {
   const repoRoot = await resolveRepoRoot(productId)
-  if (!repoRoot) return
+  if (!repoRoot) {
+    console.warn(
+      `[update_job_status] cleanup skip for job=${jobId}: no repoRoot configured for product ${productId}`,
+    )
+    return
+  }
+
+  // Branch-per-story: only remove the worktree if no sibling job in the same
+  // story is still active. If siblings are queued/claimed/running they will
+  // re-use this branch — destroying the worktree now wastes the next claim.
+  const job = await prisma.claudeJob.findUnique({
+    where: { id: jobId },
+    select: { task: { select: { story_id: true } } },
+  })
+  if (job) {
+    const activeSiblings = await prisma.claudeJob.count({
+      where: {
+        task: { story_id: job.task.story_id },
+        status: { in: ['QUEUED', 'CLAIMED', 'RUNNING'] },
+        id: { not: jobId },
+      },
+    })
+    if (activeSiblings > 0) {
+      console.log(
+        `[update_job_status] cleanup deferred for job=${jobId}: ${activeSiblings} sibling(s) still active in story ${job.task.story_id}`,
+      )
+      return
+    }
+  }
 
   // Keep branch when job is done and a branch was reported (agent pushed)
   const keepBranch = status === 'done' && branch !== undefined
   try {
     await removeWorktreeForJob({ repoRoot, jobId, keepBranch })
   } catch (err) {
-    console.warn(`[update_job_status] Worktree cleanup failed for job ${jobId}:`, err)
+    console.warn(
+      `[update_job_status] cleanup FAILED for job=${jobId} keepBranch=${keepBranch}:`,
+      err,
+    )
   }
 }
 
@@ -144,16 +175,33 @@ export async function maybeCreateAutoPr(opts: {
 
   const task = await prisma.task.findUnique({
     where: { id: taskId },
-    select: { title: true, story: { select: { code: true } } },
+    select: {
+      title: true,
+      story: { select: { id: true, code: true, title: true } },
+    },
   })
   if (!task) return null
 
-  const title = task.story.code ? `${task.story.code}: ${task.title}` : task.title
-  const body = summary
-    ? `${summary}\n\n---\n\n*Auto-generated by Scrum4Me agent*`
-    : '*Auto-generated by Scrum4Me agent*'
+  // Branch-per-story: if a sibling job in the same story already opened a PR,
+  // reuse its URL. This avoids one PR per sub-task.
+  const sibling = await prisma.claudeJob.findFirst({
+    where: {
+      task: { story_id: task.story.id },
+      pr_url: { not: null },
+      id: { not: jobId },
+    },
+    select: { pr_url: true },
+    orderBy: { created_at: 'asc' },
+  })
+  if (sibling?.pr_url) return sibling.pr_url
 
-  const result = await createPullRequest({ worktreePath, branchName, title, body })
+  // First DONE-task in the story → create a story-scoped PR
+  const storyTitle = task.story.code ? `${task.story.code}: ${task.story.title}` : task.story.title
+  const body = summary
+    ? `${summary}\n\n---\n\n*Auto-generated by Scrum4Me agent (first task in story; PR-body will accumulate as sibling tasks complete).*`
+    : '*Auto-generated by Scrum4Me agent (first task in story).*'
+
+  const result = await createPullRequest({ worktreePath, branchName, title: storyTitle, body })
   if ('url' in result) return result.url
 
   console.warn(`[update_job_status] auto-PR skipped for job ${jobId}:`, result.error)
@@ -169,14 +217,10 @@ export function registerUpdateJobStatusTool(server: McpServer) {
         'Report progress on a claimed ClaudeJob. Allowed transitions from CLAIMED/RUNNING: ' +
         'running (start), done (finished), failed (error). ' +
         'The Bearer token must match the token that claimed the job. ' +
-<<<<<<< feat/job-mgskzyvx
-        'Automatically emits an SSE event so the Scrum4Me UI updates in real time. ' +
-        'Response includes next_action: when wait_for_job_again, immediately call wait_for_job again. When queue_empty, the agent batch is done.',
-=======
         'Before marking done: call verify_task_against_plan first — done is rejected when ' +
         'verify_result is null or EMPTY (unless task.verify_only is true). ' +
-        'Automatically emits an SSE event so the Scrum4Me UI updates in real time.',
->>>>>>> main
+        'Automatically emits an SSE event so the Scrum4Me UI updates in real time. ' +
+        'Response includes next_action: when wait_for_job_again, immediately call wait_for_job again. When queue_empty, the agent batch is done.',
       inputSchema,
     },
     async ({ job_id, status, branch, summary, error }) =>