fix(test): eliminate lost-wakeup race in approval-prompt tests

The UI-approval tests drive a blocking approve_tools() by firing
resolve_approval() from a fixed 0.05s threading.Timer. approve_tools does
_approval_event.clear() -> register _pending_approval -> wait(3600s); on a
slow/loaded runner the timer can fire the event's .set() BEFORE that .clear(),
so the wakeup is wiped and approve_tools blocks the full _APPROVAL_WAIT_TIMEOUT
(one hour) -- surfacing as an intermittent CI hang (observed on the 3.12 runner
~15% into the suite; fast runners win the race, so 3.11/3.13 pass the same
commit).

Replace the fixed-delay timer with resolve_when_pending() (tests/conftest.py):
it waits until the approval is actually registered -- which happens AFTER the
clear -- before resolving, so the set can never be lost. The helper mirrors
threading.Timer's start()/cancel() so the surrounding scaffolding is unchanged.
10 sites across 3 files; the verdict-delivery timer (bounded to its own 5s
budget, not a hang) is left as-is.

Validated: the 3 files pass 20/20 under single-CPU stress (taskset -c 0) with
no hang or thread leak.

tests/conftest.py

@@ -52,8 +52,60 @@ def serve_until_exit(server: Any) -> None:
         loop.close()
 
 
+class _PendingResolver:
+    """Race-free drop-in for ``threading.Timer(delay, ui.resolve_approval)``.
+
+    ``approve_tools`` runs ``_approval_event.clear()`` -> register
+    ``_pending_approval`` -> ``_approval_event.wait(_APPROVAL_WAIT_TIMEOUT)``
+    (3600s). A *fixed-delay* timer can fire ``resolve_approval``
+    (``_approval_event.set()``) BEFORE that ``.clear()`` on a slow/loaded
+    runner, so the set is wiped by the clear and ``approve_tools`` blocks the
+    full hour -- surfacing as a CI hang. This instead waits until the approval
+    is actually registered (which happens *after* the clear), then resolves, so
+    the wakeup can never be lost. ``start()`` / ``cancel()`` mirror
+    ``threading.Timer`` so it drops into existing scaffolding; ``cancel()``
+    joins the worker (the resolve has already run or the deadline lapsed).
+    ``before`` runs just before resolving -- e.g. to snapshot pending-state
+    fields the test asserts on.
+    """
+
+    def __init__(
+        self,
+        ui: Any,
+        *args: Any,
+        before: Callable[[], None] | None = None,
+        deadline: float = 10.0,
+        **kwargs: Any,
+    ) -> None:
+        self._ui = ui
+        self._args = args
+        self._kwargs = kwargs
+        self._before = before
+        self._deadline = deadline
+        self._thread = threading.Thread(target=self._run, name="resolve-when-pending", daemon=True)
+
+    def _run(self) -> None:
+        end = time.monotonic() + self._deadline
+        while self._ui._pending_approval is None and time.monotonic() < end:
+            time.sleep(0.001)
+        if self._before is not None:
+            self._before()
+        self._ui.resolve_approval(*self._args, **self._kwargs)
+
+    def start(self) -> None:
+        self._thread.start()
+
+    def cancel(self) -> None:
+        self._thread.join(timeout=5)
+
+
+def resolve_when_pending(ui: Any, *args: Any, **kwargs: Any) -> _PendingResolver:
+    """Build a race-free approval resolver (see :class:`_PendingResolver`)."""
+    return _PendingResolver(ui, *args, **kwargs)
+
+
 if TYPE_CHECKING:
-    from collections.abc import Iterator
+    from collections.abc import Callable, Iterator
 
     from turnstone.core.mcp_client import MCPClientManager, StaticServerState
     from turnstone.core.mcp_crypto import MCPTokenCipher

tests/test_coord_ui_approve_tools.py

@@ -16,10 +16,10 @@ to ``SessionUIBase`` automatically enables:
 
 from __future__ import annotations
 
-import threading
 from typing import Any
 from unittest.mock import MagicMock, patch
 
+from tests.conftest import resolve_when_pending
 from turnstone.console.coordinator_ui import ConsoleCoordinatorUI
 
 
@@ -153,7 +153,7 @@ def test_coord_heuristic_verdict_persists_to_storage() -> None:
     items[0]["_heuristic_verdict"] = hv
 
     storage = MagicMock()
-    timer = threading.Timer(0.05, lambda: ui.resolve_approval(False))
+    timer = resolve_when_pending(ui, False)
     timer.start()
     try:
         with _patch_storage(storage):
@@ -246,9 +246,8 @@ def test_coord_pending_approval_sets_activity_tag() -> None:
     def _capture_activity() -> None:
         captured["activity"] = ui._ws_current_activity
         captured["state"] = ui._ws_activity_state
-        ui.resolve_approval(False)
 
-    timer = threading.Timer(0.05, _capture_activity)
+    timer = resolve_when_pending(ui, False, before=_capture_activity)
     timer.start()
     try:
         with _patch_storage(MagicMock()):
@@ -292,7 +291,7 @@ def test_coord_judge_pending_flag_dynamic_when_heuristic_present() -> None:
     captured_events: list[dict[str, Any]] = []
     ui._enqueue = captured_events.append  # type: ignore[method-assign]
 
-    timer = threading.Timer(0.05, lambda: ui.resolve_approval(False))
+    timer = resolve_when_pending(ui, False)
     timer.start()
     try:
         with _patch_storage(MagicMock()):
@@ -338,7 +337,7 @@ def test_coord_judge_pending_false_when_no_heuristic_verdict() -> None:
     captured_events: list[dict[str, Any]] = []
     ui._enqueue = captured_events.append  # type: ignore[method-assign]
 
-    timer = threading.Timer(0.05, lambda: ui.resolve_approval(False))
+    timer = resolve_when_pending(ui, False)
     timer.start()
     try:
         with _patch_storage(MagicMock()):
@@ -410,7 +409,7 @@ def test_coord_budget_override_prompts_even_under_blanket_auto_approve() -> None
     captured_events: list[dict[str, Any]] = []
     ui._enqueue = captured_events.append  # type: ignore[method-assign]
 
-    timer = threading.Timer(0.05, lambda: ui.resolve_approval(True))
+    timer = resolve_when_pending(ui, True)
     timer.start()
     try:
         with _patch_storage(MagicMock()):
@@ -453,7 +452,7 @@ def test_coord_budget_override_survives_wildcard_allow_policy() -> None:
     captured_events: list[dict[str, Any]] = []
     ui._enqueue = captured_events.append  # type: ignore[method-assign]
 
-    timer = threading.Timer(0.05, lambda: ui.resolve_approval(True))
+    timer = resolve_when_pending(ui, True)
     timer.start()
     try:
         with _patch_storage(MagicMock()), _patch_policies({"__budget_override__": "allow"}):

tests/test_session_ui_base.py

@@ -20,6 +20,7 @@ from unittest.mock import MagicMock, patch
 
 import pytest
 
+from tests.conftest import resolve_when_pending
 from turnstone.core.session_ui_base import SessionUIBase
 
 
@@ -1832,7 +1833,7 @@ def test_approve_tools_skips_smart_stage_when_disabled() -> None:
     ui.smart_approval_wait_seconds = 1.0
     item = _pending_item("c1")
     ui.seed_verdicts = [_llm_verdict("c1", recommendation="approve", confidence=0.99)]
-    timer = threading.Timer(0.05, lambda: ui.resolve_approval(True, "ok"))
+    timer = resolve_when_pending(ui, True, "ok")
     timer.start()
     try:
         with _patch_get_storage(storage), _patch_policies({}):
@@ -1941,7 +1942,7 @@ def test_approve_tools_reemits_verdict_after_card_on_held_batch() -> None:
     item = _pending_item("c1")
     ui.seed_verdicts = [_llm_verdict("c1", recommendation="review", confidence=0.99)]
     lq = ui._register_listener()
-    timer = threading.Timer(0.1, lambda: ui.resolve_approval(False, "no"))
+    timer = resolve_when_pending(ui, False, "no")
     timer.start()
     try:
         with _patch_get_storage(storage), _patch_policies({}):
@@ -1970,7 +1971,7 @@ def test_judge_pending_true_when_llm_verdict_not_yet_cached() -> None:
     ui = _make_ui()  # smart_approvals_enabled defaults False
     item = _pending_item("c1")  # carries _heuristic_verdict, no cached LLM verdict
     lq = ui._register_listener()
-    timer = threading.Timer(0.1, lambda: ui.resolve_approval(True, "ok"))
+    timer = resolve_when_pending(ui, True, "ok")
     timer.start()
     try:
         with _patch_get_storage(MagicMock()), _patch_policies({}):

tests/test_webui_auto_approve_visibility.py

@@ -21,12 +21,12 @@ exactly the case the visibility fix is meant to surface.
 from __future__ import annotations
 
 import queue
-import threading
 from typing import Any
 from unittest.mock import MagicMock, patch
 
 import pytest
 
+from tests.conftest import resolve_when_pending
 from turnstone.server import WebUI
 
 
@@ -107,11 +107,11 @@ def test_policy_partial_allow_then_prompt_records_allowed_items() -> None:
     ui = WebUI(ws_id="ws-test")
     items = _make_items(("c1", "read_file"), ("c2", "bash"))
 
-    # ``approve_tools`` blocks on ``_approval_event.wait`` for the
-    # prompt path.  Schedule a deny-by-operator on a tiny timer so
-    # the wait returns promptly; this test asserts on ring-buffer
-    # state, not the verdict outcome, so a deny is fine.
-    timer = threading.Timer(0.05, lambda: ui.resolve_approval(False))
+    # ``approve_tools`` blocks on ``_approval_event.wait`` for the prompt
+    # path.  Resolve (deny) once the approval is registered so the wait
+    # returns promptly without the lost-wakeup race a fixed-delay timer has;
+    # this test asserts on ring-buffer state, not the verdict, so a deny is fine.
+    timer = resolve_when_pending(ui, False)
     timer.start()
 
     storage = MagicMock()