fix: a stopped source is not a failing one, and cannot be deep-scanned (4279)

Ebi77 sat in the "1 source is failing" banner for six days with no action
available, reading `stranded by recovery sweep (no terminal status after
time_limit)`. Four things lined up:

1. The membership sweep did its job — saw `former_patron`, disabled the
   source, cleared its failure state. Clean at 02:50.
2. Twenty minutes later a deep scan was armed on it. `/backfill` had a
   credential pre-flight but NO `enabled` guard, while `/check` has carried
   one all along. The two trigger endpoints disagreed, and the ungated one is
   the one that arms the long walk.
3. Without a membership the walk cannot finish, never reaches a terminal
   status, and the recovery sweep strands it with consecutive_failures = 1.
4. Nothing could clear that. A disabled source is never scheduled, so no
   successful run resets the count; `SourceService.update` clears only on an
   explicit disable and it was already disabled; and the banner's Retry routes
   to `/check`, which refuses a disabled source. The card offered a button
   structurally incapable of acting on the only source it was showing.

`failing_sources_clause()` now means "enabled AND erroring". That also settles
a disagreement its two callers already had: the scheduler's count paired it
with `enabled.is_(True)` and `SourceService.list(failing=True)` did not, so
one counted Ebi77 and the other did not — exactly the drift the note above
that function warns about, which is why the test belongs IN the predicate
rather than beside it. The scheduler's now-duplicate clause is dropped so one
place decides.

`/backfill` gains the guard for start/recover/recapture. `stop` stays open on
a disabled source, or arming becomes a one-way door.

Migration 0101 clears failure state on sources that are already disabled — the
predicate fixes what the surfaces report, not what the rows carry, and the
rows are why the operator had no way out (lesson #4202). It matches what
`update` already does on an explicit disable, so rows disabled by any other
path come into line. Enabled sources are untouched: a real failure on a live
source must keep showing, which the second new test pins.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVjrnpQjRgHdvq95rASoiR

tests/test_source_service.py

@@ -682,3 +682,83 @@ async def test_new_disabled_source_skips_backfill(db):
         enabled=False,
     )
     assert rec.backfill_runs_remaining == 0
+
+
+@pytest.mark.asyncio
+async def test_a_disabled_source_is_not_failing(db):
+    """#4279: "stopped because you no longer subscribe" is not "failing".
+
+    Ebi77 was stopped by the membership sweep as `former_patron`, then a deep
+    scan armed on it got stranded by the recovery sweep. The banner showed it
+    for six days with no action available: a disabled source is never
+    scheduled (so no run clears the count), `update` only clears on an
+    explicit disable (it was already disabled), and Retry routes to /check,
+    which refuses a disabled source.
+    """
+    artist = await _artist(db)
+    svc = SourceService(db)
+    rec = await svc.create(
+        artist_id=artist.id, platform="patreon",
+        url="https://patreon.com/stopped",
+    )
+    source = (await db.execute(
+        select(Source).where(Source.id == rec.id)
+    )).scalar_one()
+    source.enabled = False
+    source.consecutive_failures = 1
+    source.last_error = "stranded by recovery sweep (no terminal status after time_limit)"
+    await db.commit()
+
+    assert [r.id for r in await svc.list(failing=True)] == []
+
+
+@pytest.mark.asyncio
+async def test_an_enabled_source_that_errors_is_still_failing(db):
+    """The other half — folding `enabled` in must not hide a real failure on
+    a live source."""
+    artist = await _artist(db)
+    svc = SourceService(db)
+    rec = await svc.create(
+        artist_id=artist.id, platform="patreon", url="https://patreon.com/live",
+    )
+    source = (await db.execute(
+        select(Source).where(Source.id == rec.id)
+    )).scalar_one()
+    source.enabled = True
+    source.consecutive_failures = 2
+    source.last_error = "auth failed"
+    await db.commit()
+
+    assert [r.id for r in await svc.list(failing=True)] == [rec.id]
+
+
+@pytest.mark.asyncio
+async def test_the_failing_list_and_the_ribbon_count_agree(db):
+    """The two callers of `failing_sources_clause` disagreed before #4279:
+    the scheduler's count paired it with `enabled.is_(True)`, the list did
+    not, so one counted Ebi77 and the other did not. The predicate owns the
+    whole definition now — assert the two surfaces match rather than trusting
+    that they were both updated."""
+    from backend.app.services.scheduler_service import scheduler_status
+
+    artist = await _artist(db)
+    svc = SourceService(db)
+    for url, enabled, fails in (
+        ("https://patreon.com/one", True, 3),
+        ("https://patreon.com/two", False, 1),
+        ("https://patreon.com/three", True, 0),
+    ):
+        rec = await svc.create(
+            artist_id=artist.id, platform="patreon", url=url,
+        )
+        s = (await db.execute(
+            select(Source).where(Source.id == rec.id)
+        )).scalar_one()
+        s.enabled = enabled
+        s.consecutive_failures = fails
+    await db.commit()
+
+    listed = len(await svc.list(failing=True))
+    counts = await scheduler_status(db)
+    assert listed == 1
+    assert counts["failing_sources"] == listed