feat(ledger): reason codes, case-insensitive repo filter, next action on the coverage line (#2874, milestone 294)

- code_shapes.reason_code (migration 0083): an optional code from a fixed
  catalogue (scoped-css, one-off-handler, test-helper, convention-plumbing,
  pure-helper, generated, script, typed-record) beside the prose reason, so
  the ledger can be filtered/aggregated by kind of one-off; validated in
  classify_shapes and classify_shapes_by_rule; on to_dict/to_compact.
- Snippet location lookups match repo case-insensitively in both dialects
  (location_matches / location_jsonpath via like_regex flag "i") — "Scribe"
  vs "FabledScribe" vs "fabledscribe" recorded free-form hid half the canon
  from list_snippets(repo=, path=).
- coverage line names the next action: "top canon #N ×k" (biggest proposal
  queue) and "top copy <label> ×files" (widest body-identical group).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_pattern_coverage.py

@@ -497,6 +497,12 @@ def test_coverage_line_names_the_proposers_standing():
     assert "; 90 unclassified (40 proposed, 2 derive groups), largest: src" in line
     line = coverage_line({**base, "proposed": 0, "derive_groups": [{"group": "a"}]})
     assert "(1 derive group)" in line
+    # #2874: the next action on the line — biggest canon queue, widest copy.
+    line = coverage_line({
+        **base, "proposed": 40, "top_canon": {"snippet_id": 2844, "count": 78},
+        "derive_groups": [{"group": "dup:abc", "label": "closed-msg (identical body)", "files": 3}],
+    })
+    assert "top canon #2844 ×78" in line and "top copy closed-msg (identical body) ×3 files" in line
 
 
 def test_coverage_line_names_divergence_and_recheck():

tests/test_shape_ledger.py

@@ -391,6 +391,22 @@ def test_compact_row_carries_identity_standing_and_the_proposers_word_only():
         assert noisy not in compact
 
 
+def test_reason_codes_are_a_fixed_catalogue_and_validated():
+    """#2874: an optional index beside the prose reason; unknown codes are a
+    structural error (the batch applies nothing)."""
+    from scribe.models.code_shape import REASON_CODES
+    from scribe.services.shape_ledger import validate_classifications
+    assert set(REASON_CODES) == {
+        "scoped-css", "one-off-handler", "test-helper", "convention-plumbing",
+        "pure-helper", "generated", "script", "typed-record",
+    }
+    assert "reason_code" in CodeShape.__table__.c
+    ok = [{"path": "a.py", "symbol": "f", "status": "exempt", "reason": "x", "reason_code": "pure-helper"}]
+    assert validate_classifications(ok) is None
+    bad = [{"path": "a.py", "symbol": "f", "status": "exempt", "reason": "x", "reason_code": "nope"}]
+    assert "unknown reason_code" in validate_classifications(bad)
+
+
 def test_rule_matches_is_directory_glob_and_kind_aware():
     from scribe.models.code_shape import CodeShape
     from scribe.services.shape_ledger import rule_matches

tests/test_snippet_location_filter.py

@@ -56,6 +56,7 @@ def test_no_parts_matches_everything():
 def test_matches_exact_repo_path_and_symbol():
     data = _data({"repo": "Scribe", "path": "src/scribe/x.py", "symbol": "helper"})
     assert location_matches(data, {"repo": "Scribe"})
+    assert location_matches(data, {"repo": "scribe"})   # repo names: case never distinguishes (#2874)
     assert location_matches(data, {"path": "src/scribe/x.py"})
     assert location_matches(data, {"symbol": "helper"})
     assert location_matches(data, {"repo": "Scribe", "symbol": "helper"})
@@ -101,7 +102,8 @@ def test_blank_recorded_part_does_not_match_a_requested_one():
 def test_jsonpath_filters_within_one_locations_entry():
     expr = location_jsonpath({"repo": "Scribe", "symbol": "helper"})
     assert expr.startswith("$.locations[*] ? (")
-    assert '@.repo == "Scribe"' in expr
+    # repo: anchored, case-insensitive (#2874) — mirrors location_matches.
+    assert '@.repo like_regex "^Scribe$" flag "i"' in expr
     assert '@.symbol == "helper"' in expr
     assert " && " in expr
 
@@ -121,8 +123,9 @@ def test_jsonpath_quotes_values_as_json_literals():
     """A quote in a repo name must stay inside the literal, not end it."""
     nasty = 'we"ird'
     expr = location_jsonpath({"repo": nasty})
-    assert json.dumps(nasty) in expr
+    assert json.dumps("^" + nasty + "$") in expr      # the regex is a JSON literal too
     assert '\\"' in expr
+    assert json.dumps(nasty) in location_jsonpath({"symbol": nasty})
 
 
 def test_jsonpath_emits_parts_in_a_fixed_key_order():