fix(dolt): record/alert revision-detection failures + handle cancellation

Review fixes to the import-run framework (A1):

1. detect_revision ran outside the failure handler, so a failed revision probe
   (the most likely external failure) escaped unrecorded — violating "every
   attempt is recorded". Now the running row is created FIRST, then
   detect_revision + last-revision lookup + stage + validate + promote all run
   inside the same handler; the row converts to no_op when the revision is
   unchanged. New test covers a detection exception → recorded failed + alert.

2. asyncio.CancelledError (BaseException, not caught by except Exception) left a
   permanent running row on deploy/scheduler shutdown. Now caught explicitly:
   best-effort mark failed, then re-raise the cancellation (never swallowed).
   New test asserts the run is failed and the error re-propagates.

Full suite 682 passed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/unit/test_data_import_framework.py

@@ -14,6 +14,7 @@ sequenced around the ``run_import`` call.
 
 from __future__ import annotations
 
+import asyncio
 import os
 import tempfile
 from datetime import date, datetime, timezone
@@ -83,6 +84,8 @@ class FakeImporter:
         self.staged_called = True
         if self.raise_in == "stage":
             raise RuntimeError("boom-stage")
+        if self.raise_in == "cancel":
+            raise asyncio.CancelledError()
         return list(range(self.n_rows))
 
     async def validate(self, db, staged):
@@ -199,3 +202,32 @@ async def test_exception_in_promote_rolls_back(engine):
     assert "boom-promote" in (run.error_details or "")
     assert await _count(factory, FundamentalSnapshot) == 3  # partial write rolled back
     assert await _count(factory, SystemEvent) == 1
+
+
+async def test_detection_failure_records_and_alerts(engine):
+    """The external revision probe is the most likely failure — it must produce a
+    recorded failed run + alert, not an unrecorded escaping exception."""
+    factory = _factory(engine)
+    imp = FakeImporter("rev1", raise_in="detect")
+
+    run = await run_import(imp, engine=engine)
+
+    assert run is not None and run.status == STATUS_FAILED
+    assert "boom-detect" in (run.error_details or "")
+    assert imp.staged_called is False
+    assert await _count(factory, FundamentalSnapshot) == 0
+    assert await _count(factory, SystemEvent) == 1  # alerted
+    runs = await _runs(factory)
+    assert len(runs) == 1 and runs[0].status == STATUS_FAILED  # attempt recorded
+
+
+async def test_cancellation_marks_failed_and_reraises(engine):
+    factory = _factory(engine)
+
+    with pytest.raises(asyncio.CancelledError):
+        await run_import(FakeImporter("rev1", raise_in="cancel"), engine=engine)
+
+    runs = await _runs(factory)
+    assert len(runs) == 1 and runs[0].status == STATUS_FAILED  # no lingering running row
+    assert runs[0].error_details == "cancelled"
+    assert await _count(factory, FundamentalSnapshot) == 0