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>

src/scribe/mcp/tools/shapes.py

@@ -36,10 +36,14 @@ async def classify_shapes(
     Args:
         project_id: The project whose ledger is being judged.
         classifications: Objects of {path, symbol, status, kind?, snippet_id?,
-            reason?}. path+symbol name the shape exactly as list_shapes shows
-            it; kind ("sym"/"css") narrows when one file defines both.
-            snippet_id is required for canonical/instance/variant; reason is
-            required for variant/exempt.
+            reason?, reason_code?}. path+symbol name the shape exactly as
+            list_shapes shows it; kind ("sym"/"css") narrows when one file
+            defines both. snippet_id is required for canonical/instance/
+            variant; reason is required for variant/exempt. reason_code is
+            an OPTIONAL index beside the prose (one of: scoped-css,
+            one-off-handler, test-helper, convention-plumbing, pure-helper,
+            generated, script, typed-record) so the ledger can be filtered
+            and aggregated by kind of one-off — the prose stays the record.
         via: Who is judging — "agent" (default), "audit" (a sweep), or
             "import" (carrying maps recorded elsewhere).
 
@@ -145,6 +149,7 @@ async def classify_shapes_by_rule(
     reason: str = "",
     via: str = "agent",
     include_judged: bool = False,
+    reason_code: str = "",
 ) -> dict:
     """The sweep form of classify_shapes: ONE judgment applied to every
     unclassified shape under a directory whose symbol matches a glob.
@@ -167,6 +172,8 @@ async def classify_shapes_by_rule(
         snippet_id: Required for instance/variant — the canon judged against.
         reason: Required for variant/exempt — the why, recorded on every row.
         via: "agent" (default) | "audit" | "import".
+        reason_code: Optional catalogue code beside the reason (see
+            classify_shapes) — a sweep is exactly where one applies.
         include_judged: By default only unjudged rows are touched —
             `unclassified` and the sync's mechanical `scoped` stamp — a
             sweep never silently overwrites a judgment. True re-judges every
@@ -184,6 +191,7 @@ async def classify_shapes_by_rule(
             uid, project_id, path=path, status=status, pattern=pattern,
             kind=kind, snippet_id=snippet_id or None, reason=reason or None,
             via=via, include_judged=include_judged,
+            reason_code=reason_code or None,
         )
     except ValueError as exc:
         return {"error": str(exc)}