PBI-50: SPRINT_IMPLEMENTATION single-session sprint runner (Scrum4Me-side) (#139)

* PBI-50 F1: SPRINT_BATCH execution-strategy + cross-repo blocker + branch-resume

Schema-migratie + Scrum4Me-side wiring voor de nieuwe SPRINT_IMPLEMENTATION-flow:

- prisma: PrStrategy ADD VALUE 'SPRINT_BATCH'; ClaudeJobKind ADD VALUE
  'SPRINT_IMPLEMENTATION'; nieuwe enum SprintTaskExecutionStatus; ClaudeJob.lease_until
  + status_lease_until index; SprintRun.previous_run_id (self-relation
  SprintRunChain) voor branch-hergebruik bij resume; nieuwe sprint_task_executions
  tabel met frozen plan_snapshot + verify_required_snapshot per task in scope.
- actions/sprint-runs.ts startSprintRunCore: nieuwe blocker-type 'task_cross_repo'
  voor SPRINT_BATCH (pre-flight rejecteert sprints met cross-repo task_url).
  Bij SPRINT_BATCH: één SPRINT_IMPLEMENTATION ClaudeJob (geen per-task loop).
- actions/sprint-runs.ts resumePausedSprintRunAction: SPRINT_BATCH-pad met
  remaining-execution-check; bij onafgemaakt werk → nieuwe SprintRun met
  previous_run_id + run.branch hergebruikt + nieuwe SPRINT_IMPLEMENTATION-job.
  Oude SprintRun → CANCELLED. Bestaande PBI-49 P0 scope-DONE pad ongewijzigd.
- actions/products.ts updatePrStrategyAction: accepteert SPRINT_BATCH.
- components/products/pr-strategy-select.tsx: drie opties met helptekst,
  gebruikt @prisma/client PrStrategy ipv lokaal type.
- components/sprint/sprint-run-controls.tsx: BLOCKER_LABELS + blockerHref
  voor task_cross_repo.

Migratie applied op Neon. Type-check + 532 tests groen.

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

* PBI-50 F5: cross-repo blocker test voor SPRINT_BATCH

- task_cross_repo blocker fires bij task.repo_url ≠ product.repo_url
- happy path: tasks zonder repo_url-override of met match → één
  SPRINT_IMPLEMENTATION-job (niet per-task).

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

* PBI-50 F5: docs/architecture/sprint-execution-modes.md

Vergelijking PER_TASK vs SPRINT_BATCH met trade-offs, datamodel-
toevoegingen (SprintTaskExecution, lease_until, SprintRunChain) en
MCP-tools-matrix per modus. Toegevoegd aan breadcrumb in
docs/architecture.md.

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

---------

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

__tests__/actions/sprint-runs.test.ts

@@ -201,6 +201,106 @@ describe('startSprintRunAction — pre-flight blockers', () => {
   })
 })
 
+describe('startSprintRunAction — SPRINT_BATCH', () => {
+  const SPRINT_BATCH = {
+    ...SPRINT_OK,
+    product: {
+      id: 'prod-1',
+      pr_strategy: 'SPRINT_BATCH',
+      repo_url: 'https://github.com/example/main',
+    },
+  }
+
+  it('blokkeert task met afwijkende repo_url', async () => {
+    mockPrisma.sprint.findUnique.mockResolvedValue(SPRINT_BATCH)
+    mockPrisma.sprintRun.findFirst.mockResolvedValue(null)
+    mockPrisma.story.findMany.mockResolvedValue([
+      {
+        ...STORY_OK,
+        tasks: [
+          {
+            id: 'task-1',
+            code: 'T-1',
+            title: 'In main repo',
+            priority: 1,
+            sort_order: 1,
+            implementation_plan: 'plan',
+            repo_url: null,
+          },
+          {
+            id: 'task-2',
+            code: 'T-2',
+            title: 'Cross-repo',
+            priority: 1,
+            sort_order: 2,
+            implementation_plan: 'plan',
+            repo_url: 'https://github.com/example/other',
+          },
+        ],
+      },
+    ])
+    mockPrisma.claudeQuestion.findMany.mockResolvedValue([])
+
+    const result = await startSprintRunAction({ sprint_id: 'sprint-1' })
+
+    expect(result).toMatchObject({ ok: false, error: 'PRE_FLIGHT_BLOCKED' })
+    if (result.ok === false && 'blockers' in result) {
+      expect(result.blockers).toContainEqual({
+        type: 'task_cross_repo',
+        id: 'task-2',
+        label: 'T-2: Cross-repo',
+      })
+    }
+    expect(mockPrisma.sprintRun.create).not.toHaveBeenCalled()
+  })
+
+  it('staat tasks toe wanneer repo_url leeg is of gelijk aan product.repo_url', async () => {
+    mockPrisma.sprint.findUnique.mockResolvedValue(SPRINT_BATCH)
+    mockPrisma.sprintRun.findFirst.mockResolvedValue(null)
+    mockPrisma.story.findMany.mockResolvedValue([
+      {
+        ...STORY_OK,
+        tasks: [
+          {
+            id: 'task-1',
+            code: 'T-1',
+            title: 'No override',
+            priority: 1,
+            sort_order: 1,
+            implementation_plan: 'plan',
+            repo_url: null,
+          },
+          {
+            id: 'task-2',
+            code: 'T-2',
+            title: 'Same repo',
+            priority: 1,
+            sort_order: 2,
+            implementation_plan: 'plan',
+            repo_url: 'https://github.com/example/main',
+          },
+        ],
+      },
+    ])
+    mockPrisma.claudeQuestion.findMany.mockResolvedValue([])
+    mockPrisma.sprintRun.create.mockResolvedValue({ id: 'run-batch' })
+    mockPrisma.claudeJob.create.mockResolvedValue({ id: 'job-sprint' })
+
+    const result = await startSprintRunAction({ sprint_id: 'sprint-1' })
+
+    expect(result).toMatchObject({ ok: true, sprint_run_id: 'run-batch' })
+    // Eén SPRINT_IMPLEMENTATION-job, niet per-task
+    expect(mockPrisma.claudeJob.create).toHaveBeenCalledTimes(1)
+    expect(mockPrisma.claudeJob.create).toHaveBeenCalledWith({
+      data: expect.objectContaining({
+        kind: 'SPRINT_IMPLEMENTATION',
+        sprint_run_id: 'run-batch',
+        product_id: 'prod-1',
+      }),
+    })
+  })
+})
+
 describe('startSprintRunAction — guards', () => {
   it('weigert wanneer Sprint niet ACTIVE is', async () => {
     mockPrisma.sprint.findUnique.mockResolvedValue({ ...SPRINT_OK, status: 'COMPLETED' })