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/tests/test_engine_flow.py

@@ -14,7 +14,8 @@ git (in-memory ``FakeRepoWorkspace``) are fakes. What it defends:
 * red tests and a forbidden diff send the work *back* with cycle + 1 instead of
   merging it
 * ``analysis_only`` never creates a worktree
-* an overdrawn wallet pauses the task before a single turn is spent
+* an empty, overdrawn or missing wallet pauses the task before a single turn is
+  spent (prepaid billing, decision D-B)
 * a transient provider failure is retried, then handed to the manager
 """
 
@@ -92,13 +93,19 @@ class _OverdrawnWallet:
 
 
 class _ZeroWallet:
-    """A wallet at exactly zero: the normal starting state of a fresh, post-paid org."""
+    """A wallet at exactly zero: prepaid, so no credit is left."""
 
     balance = 0.0
 
 
+class _FundedWallet:
+    """A wallet with credit left: the org may spend a turn."""
+
+    balance = 5.0
+
+
 class _Wallets:
-    def __init__(self, wallet: _OverdrawnWallet | _ZeroWallet | None) -> None:
+    def __init__(self, wallet: _OverdrawnWallet | _ZeroWallet | _FundedWallet | None) -> None:
         self._wallet = wallet
 
     async def get_for_org(self, organization_id: str):
@@ -567,14 +574,12 @@ async def test_an_overdrawn_wallet_pauses_the_task_before_a_turn_is_spent(
     assert BUDGET_PAUSED_MESSAGE
 
 
-async def test_a_zero_wallet_does_not_pause_a_fresh_org(world, session_factory):
-    """A 0.0 balance is every org's starting state, so it must not pause the task.
+async def test_a_zero_wallet_pauses_the_task_before_a_turn_is_spent(world, session_factory):
+    """A zero balance is no credit left: the task pauses before a turn is spent.
 
-    This is an intentional behaviour change. The scheduler used to pause on
-    ``balance <= 0``, which froze every new org before its first turn: usage is
-    post-paid and nothing debits a wallet. Only an overdrawn wallet (below zero)
-    pauses now. The old test that encoded the previous rule was renamed and
-    updated, as PLAN-v2 §7.4 requires for a deliberate behaviour change.
+    Prepaid billing (decision D-B) reverses the post-paid rule of the earlier plan
+    (its T3), under which a zero balance was every new org's normal state and did
+    not pause. Now the platform owner credits an org before any work runs.
     """
     scripted = ScriptedModel([ScriptedReply(content="[[ASSIGN/]]")])
     workspace = FakeRepoWorkspace()
@@ -594,6 +599,58 @@ async def test_a_zero_wallet_does_not_pause_a_fresh_org(world, session_factory):
         )
         await _run(scheduler, session, 1)
         state = await PipelineStateRepository(session).get(row.id)
+        task = await TaskRepository(session).get(row.id)
+
+    assert state is not None and state.stage is Stage.PAUSED
+    assert task is not None and task.status is TaskStatus.WAITING_APPROVAL
+    assert scripted.calls == 0
+
+
+async def test_a_missing_wallet_pauses_the_task(world, session_factory):
+    """No wallet row at all counts as zero credit (prepaid): the task pauses."""
+    scripted = ScriptedModel([ScriptedReply(content="[[ASSIGN/]]")])
+    workspace = FakeRepoWorkspace()
+    async with session_factory() as session:
+        await _team(session, world)
+        row = await _task(session, world, stage=Stage.PENDING_MANAGER_REVIEW)
+        await session.commit()
+        scheduler = _scheduler(
+            session,
+            world,
+            scripted=scripted,
+            sandbox=FakeSandbox(),
+            workspace=workspace,
+            memory=RecordingMemory(),
+            delivery=NullDeliveryHooks(),
+            wallets=_Wallets(None),
+        )
+        await _run(scheduler, session, 1)
+        state = await PipelineStateRepository(session).get(row.id)
+
+    assert state is not None and state.stage is Stage.PAUSED
+    assert scripted.calls == 0
+
+
+async def test_a_funded_wallet_does_not_pause(world, session_factory):
+    """Credit left means the org may spend a turn: the task is not paused."""
+    scripted = ScriptedModel([ScriptedReply(content="[[ASSIGN/]]")])
+    workspace = FakeRepoWorkspace()
+    async with session_factory() as session:
+        await _team(session, world)
+        row = await _task(session, world, stage=Stage.PENDING_MANAGER_REVIEW)
+        await session.commit()
+        scheduler = _scheduler(
+            session,
+            world,
+            scripted=scripted,
+            sandbox=FakeSandbox(),
+            workspace=workspace,
+            memory=RecordingMemory(),
+            delivery=NullDeliveryHooks(),
+            wallets=_Wallets(_FundedWallet()),
+        )
+        await _run(scheduler, session, 1)
+        state = await PipelineStateRepository(session).get(row.id)
 
     assert state is not None and state.stage is not Stage.PAUSED
     assert scripted.calls == 1