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

tests/test_gate_settings.py

@@ -0,0 +1,78 @@
+"""The create gate's similarity bars are settings, clamped and fail-open (#4385)."""
+from unittest.mock import AsyncMock, patch
+
+import pytest
+
+from scribe.services.dedup import (
+    _GATE_MIN_BLOCK,
+    _GATE_MIN_OVERLAP,
+    GATE_DEFAULT_THRESHOLDS,
+    _gate_setting,
+)
+
+# Bound at import, before the autouse stub in conftest replaces the module
+# attribute — so these tests exercise the real read.
+_real_gate_setting = _gate_setting
+
+
+def _setting(value):
+    return patch("scribe.services.settings.get_setting", AsyncMock(return_value=value))
+
+
+@pytest.mark.asyncio
+async def test_a_set_value_is_used():
+    with _setting("0.95"):
+        assert await _real_gate_setting(7, "note_copy", _GATE_MIN_BLOCK) == 0.95
+
+
+@pytest.mark.asyncio
+async def test_a_block_bar_cannot_be_set_low_enough_to_refuse_everything():
+    with _setting("0.1"):
+        assert await _real_gate_setting(7, "general", _GATE_MIN_BLOCK) == _GATE_MIN_BLOCK
+
+
+@pytest.mark.asyncio
+async def test_the_overlap_floor_has_its_own_lower_clamp():
+    with _setting("0.1"):
+        assert await _real_gate_setting(7, "note_overlap", _GATE_MIN_OVERLAP) == _GATE_MIN_OVERLAP
+
+
+@pytest.mark.asyncio
+async def test_an_unparseable_value_falls_back_to_the_default():
+    with _setting("lots"):
+        got = await _real_gate_setting(7, "snippet", _GATE_MIN_BLOCK)
+    assert got == GATE_DEFAULT_THRESHOLDS["snippet"]
+
+
+@pytest.mark.asyncio
+async def test_an_unreadable_setting_falls_back_to_the_default():
+    with patch("scribe.services.settings.get_setting",
+               AsyncMock(side_effect=RuntimeError("db down"))):
+        got = await _real_gate_setting(7, "lesson", _GATE_MIN_BLOCK)
+    assert got == GATE_DEFAULT_THRESHOLDS["lesson"]
+
+
+@pytest.mark.asyncio
+async def test_the_overlap_floor_never_sits_above_the_block_bar():
+    from scribe.services.dedup import gate_bars
+
+    async def _set(user_id, key, lo):
+        return {"note_copy": 0.85, "note_overlap": 0.90}[key]
+
+    with patch("scribe.services.dedup._gate_setting", AsyncMock(side_effect=_set)):
+        assert await gate_bars(7, "note") == (0.85, 0.85)
+
+
+@pytest.mark.asyncio
+async def test_a_kind_outside_the_copy_band_reads_no_overlap_floor():
+    from scribe.services.dedup import gate_bars
+
+    seen = []
+
+    async def _set(user_id, key, lo):
+        seen.append(key)
+        return GATE_DEFAULT_THRESHOLDS[key]
+
+    with patch("scribe.services.dedup._gate_setting", AsyncMock(side_effect=_set)):
+        assert await gate_bars(7, "process") == (0.90, 0.90)
+    assert seen == ["general"]