feat(dedup): the create gate's similarity bars are settings (#4385, rule 25)

gate_bars(user_id, note_type) resolves the block bar and, for notes and
tasks, the overlap floor from kb_gate_* settings, with the old constants
as defaults. Fail-open on an unreadable value; a block bar clamps at 0.80
and the overlap floor at 0.70 and never above the bar. Five fields in
Settings beside the duplicate-report floors.

CLAIM_LEASE stays a constant, with the reason written at it: a per-user
lease would make one shared task live to one reader and dead to another.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/conftest.py

@@ -178,3 +178,24 @@ def _no_rule_overlap():
     with patch("scribe.services.dedup.find_overlapping_rules",
                AsyncMock(return_value=[])):
         yield
+
+
+@pytest.fixture(autouse=True)
+def _default_gate_bars():
+    """Read the create gate's bars as their defaults, not from settings (#4385).
+
+    Every create through the note gate now asks the user's settings for its
+    similarity bars, which is a database read on a path the gate's unit tests
+    run without one. Stubbed one level down — `_gate_setting`, not `gate_bars`
+    — so the copy-band logic above it (which kinds read an overlap floor, the
+    floor never sitting above the bar) still runs in every test. The setting
+    read itself is tested in tests/test_gate_settings.py, which binds the real
+    function at import time, before this patch runs.
+    """
+    from scribe.services.dedup import GATE_DEFAULT_THRESHOLDS
+
+    async def _default(user_id, key, lo):
+        return GATE_DEFAULT_THRESHOLDS[key]
+
+    with patch("scribe.services.dedup._gate_setting", AsyncMock(side_effect=_default)):
+        yield