feat(dedup): the duplicate report reaches notes and tasks, with per-kind cures

Step 5 of #278, folding in #2534. The operator's no-gate decision for the web
UI (#2482 — "an llm attached to this surface is the corrections system") has a
precondition nobody had built: the corrector has to be able to SEE what needs
correcting. find_duplicate_snippets had no equivalent for notes or tasks, so a
duplicate note was only ever noticed by accident.

find_duplicate_records(kind="snippet"|"note"|"task") — the same indexed
self-join, parameterised. Tasks are notes with a status, not a note_type, so
the kind split is a status predicate; mixing them would propose folding a
to-do into a write-up. find_duplicate_snippets stays as a wrapper because both
surfaces and SnippetListView consume it by name.

What differs by kind is the CURE, and the report says so in a `suggestion`
field rather than leaving the caller to guess:

  snippet  merge — lossless, the survivor keeps every call site
  note     NEVER merge. A correction pair → supersedes on the newer; state
           smeared across dated records → extract to the System's reference
           note; genuinely parallel → leave alone. Choosing needs the records
           READ, which is the agent's job — so non-snippet groups carry
           `members` with dates and any `existing_supersessions` already
           declared inside the group. A pair someone ruled on is not an open
           question.
  task     usually the same work opened twice — keep the one with the history,
           cancel the other with a pointer.

The snippet sibling filter stays snippet-only: it keys on symbol/code_sha,
which other kinds don't carry — and for them a look-alike is a finding.

Surfaces: MCP find_duplicate_records (classified into _READ_ONLY_TOOLS — the
completeness test would have caught the omission), REST /api/notes/duplicates,
and a KnowledgeView panel mirroring SnippetListView's — links only, no merge
button, because for notes the report proposes and the correction is a read-
and-decide act. The panel follows the type filter and clears when it changes,
so a note report can't linger under a task view.

Correcting the task's own premise: it claimed the snippet report had "no view
consuming it" — stale; SnippetListView has consumed it since it shipped. The
UI gap was only ever notes/tasks.

Answers the question carried from #2482: yes, the update routes on BOTH
surfaces can turn a record into a duplicate — the gate is create-time by
design. This report is the mechanism that catches it after the fact, which is
the model the operator chose.

Refs #278, #2547

tests/test_services_dedup.py

@@ -282,3 +282,46 @@ def test_duplicate_response_names_what_matched_for_structural_hits():
         DuplicateMatch(id=9, title="x", similarity=1.0, reason="code"), "snippet",
     )
     assert "identical code" in r["message"]
+
+
+# --- the generalised report (#2547) ------------------------------------------
+
+
+@pytest.mark.asyncio
+async def test_report_refuses_an_unknown_kind():
+    """A typo'd kind must fail loudly, not scan snippets by default — the
+    caller asked a question about a kind that doesn't exist, and answering a
+    different question instead is how wrong conclusions get confident."""
+    from scribe.services.dedup import find_duplicate_records
+
+    with pytest.raises(ValueError, match="kind must be one of"):
+        await find_duplicate_records(7, kind="rule")
+
+
+def test_kind_clauses_split_notes_from_tasks_on_status():
+    """Tasks are notes with a status, not a note_type of their own. A report
+    that mixed them would propose folding a to-do into a write-up."""
+    from scribe.models.note import Note
+    from scribe.services.dedup import _kind_clauses
+
+    note_sql = " AND ".join(str(c) for c in _kind_clauses("note", Note))
+    task_sql = " AND ".join(str(c) for c in _kind_clauses("task", Note))
+    snip_sql = " AND ".join(str(c) for c in _kind_clauses("snippet", Note))
+
+    assert "status IS NULL" in note_sql
+    assert "status IS NOT NULL" in task_sql
+    assert "note_type" in snip_sql and "status" not in snip_sql
+
+
+def test_every_kind_has_a_suggestion_and_none_proposes_merging_notes():
+    """The suggestion is the report's point: what to DO differs by what the
+    records are, and 'merge' is only ever the answer for snippets — folding two
+    notes destroys what each said, which is why consolidated_at was dropped
+    rather than built (#2483)."""
+    from scribe.services.dedup import _KIND_SUGGESTION, _REPORT_KINDS
+
+    for kind in _REPORT_KINDS:
+        assert _KIND_SUGGESTION.get(kind), f"no suggestion for {kind}"
+    assert "merge" in _KIND_SUGGESTION["snippet"]
+    assert "NOT merge" in _KIND_SUGGESTION["note"]
+    assert "supersedes" in _KIND_SUGGESTION["note"]