feat(integration): prepaid billing, engine UI, credits console, direct tasks, v2 final

- Prepaid credit system: org wallet, debit on usage, chat gate, admin credit console
- Engine UI: /manager, /tasks, /tasks/[id], /workforce, /dashboard, /traces pages
- Direct task creation (HTTP POST /tasks, MCP tasks_create) at pending_manager_review
- Pause/resume/cancel/answer actions in engine API and UI
- Employee cap (7 per org default), review pipeline guard (active reviewer required)
- Scheduler: wide window prevents org starvation; archived employees excluded from cap
- Tenant isolation: project-id cross-org 404, engine never uses another tenant's sandbox
- Order route fix: manager built with pipeline states + employee profiles
- Contract extension: ModelGrantPort.get_org_policy with DefaultOrgPolicy
- Engine event types in @agy/contracts (task.step, task.gate, run.log, run.tool, team.changed)
- api-engine.ts typed client; api-credit.ts client
- Alembic migration c4d5e6f7a8b9: prepaid credit + engine UI tables
- 859 tests passed, 1 skipped; ruff/mypy/tsc/eslint/vitest all green

Refs: PLAN-v2.md §9 (T1–T43), todo-v2-final.md

apps/api/app/application/engine/events.py

@@ -28,6 +28,7 @@ from app.application.ports.realtime import (
     task_channel,
 )
 from app.core.config import settings
+from app.domain.workforce.pipeline import PipelineKey, Stage, coarse_status
 
 
 @dataclass(slots=True, kw_only=True)
@@ -204,4 +205,33 @@ async def emit_team_changed(
     )
 
 
-__all__ = ["RunFeed", "emit_team_changed"]
+async def emit_task_step(
+    *,
+    task_id: str,
+    organization_id: str,
+    from_stage: Stage,
+    to_stage: Stage,
+    pipeline: PipelineKey,
+) -> None:
+    """A task moved one stage: the task page's stepper follows it live.
+
+    The payload carries stage names and the coarse status only, never a model
+    or an employee name.
+    """
+    await publish(
+        RealtimeEvent(
+            type="task.step",
+            channels=(task_channel(task_id), org_channel(organization_id)),
+            organization_id=organization_id,
+            data={
+                "task_id": task_id,
+                "from": str(from_stage),
+                "to": str(to_stage),
+                "pipeline": str(pipeline),
+                "status": coarse_status(to_stage).value,
+            },
+        )
+    )
+
+
+__all__ = ["RunFeed", "emit_task_step", "emit_team_changed"]