feat(dedup): per-kind duplicate-report floors — notes/tasks default 0.93

At chunk grain (#280) a note-pair's similarity is its closest chunk pair,
so the shared 0.82 floor saturated the note/task reports with related
families (38 note / 155 task groups against the 200-pair cap, measured
2026-08-09). Split kb_duplicate_threshold into per-kind settings keys
with per-kind defaults: snippet 0.82 (single-chunk, scale unchanged),
note/task 0.93 (points the report at genuinely-alike records). Settings
UI grows the two new knobs; report entrypoints inherit the change via
get_duplicate_threshold(user_id, kind).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UaYUaouG9jjhATyuxCKrQs

tests/test_snippet_duplicates.py

@@ -10,7 +10,7 @@ import pytest
 
 from scribe.services import dedup as dedup_svc
 from scribe.services.dedup import (
-    DUPLICATE_DEFAULT_THRESHOLD,
+    DUPLICATE_DEFAULT_THRESHOLDS,
     get_duplicate_threshold,
     group_pairs,
 )
@@ -61,29 +61,52 @@ def test_a_node_never_forms_a_group_with_itself():
 # --- threshold ------------------------------------------------------------
 
 
-async def test_threshold_falls_back_to_the_default_when_unset():
+@pytest.mark.parametrize("kind", ["snippet", "note", "task"])
+async def test_threshold_falls_back_to_the_per_kind_default_when_unset(kind):
+    default = DUPLICATE_DEFAULT_THRESHOLDS[kind]
     with patch("scribe.services.settings.get_setting",
-               AsyncMock(return_value=str(DUPLICATE_DEFAULT_THRESHOLD))):
-        assert await get_duplicate_threshold(1) == DUPLICATE_DEFAULT_THRESHOLD
+               AsyncMock(return_value=str(default))):
+        assert await get_duplicate_threshold(1, kind) == default
+
+
+async def test_each_kind_reads_its_own_settings_key():
+    """Tuning the note floor must not move the snippet report — the whole
+    point of splitting the setting is that the kinds calibrate independently."""
+    get = AsyncMock(return_value="0.5")
+    with patch("scribe.services.settings.get_setting", get):
+        await get_duplicate_threshold(1, "note")
+    key, default = get.await_args.args[1], get.await_args.args[2]
+    assert key == "kb_duplicate_threshold_note"
+    assert default == str(DUPLICATE_DEFAULT_THRESHOLDS["note"])
 
 
 async def test_a_garbage_setting_falls_back_rather_than_raising():
     with patch("scribe.services.settings.get_setting",
                AsyncMock(return_value="not-a-number")):
-        assert await get_duplicate_threshold(1) == DUPLICATE_DEFAULT_THRESHOLD
+        assert (await get_duplicate_threshold(1, "snippet")
+                == DUPLICATE_DEFAULT_THRESHOLDS["snippet"])
 
 
 @pytest.mark.parametrize("stored, expected", [("2.5", 1.0), ("-3", 0.0)])
 async def test_threshold_is_clamped_to_the_valid_range(stored, expected):
     with patch("scribe.services.settings.get_setting", AsyncMock(return_value=stored)):
-        assert await get_duplicate_threshold(1) == expected
+        assert await get_duplicate_threshold(1, "snippet") == expected
 
 
-def test_the_report_threshold_is_looser_than_the_write_gate():
-    """The gate BLOCKS a create and must be unforgiving of noise; this only
-    suggests a merge the operator reviews, so it has to reach further or it
-    would never surface the pairs the gate already let through."""
-    assert DUPLICATE_DEFAULT_THRESHOLD < dedup_svc._SEMANTIC_THRESHOLD
+def test_the_snippet_report_threshold_is_looser_than_the_write_gate():
+    """The gate BLOCKS a create and must be unforgiving of noise; the snippet
+    report only suggests a merge the operator reviews, so it has to reach
+    further or it would never surface the pairs the gate already let through.
+    Snippet-only on purpose: note/task floors sit ABOVE the gate because chunk
+    grain (#280) lifts related families over it — see the module comment."""
+    assert DUPLICATE_DEFAULT_THRESHOLDS["snippet"] < dedup_svc._SEMANTIC_THRESHOLD
+
+
+def test_the_note_and_task_floors_are_stricter_than_the_snippet_floor():
+    """At chunk grain, 0.82 is a related-families view; the report's default
+    must point at genuinely-alike records (measured 2026-08-09, note #2551)."""
+    assert DUPLICATE_DEFAULT_THRESHOLDS["note"] == 0.93
+    assert DUPLICATE_DEFAULT_THRESHOLDS["task"] == 0.93
 
 
 # --- fail-open ------------------------------------------------------------