feat(coverage): the line names standing work with 0 unclassified + derive_new, copies that joined a family since the previous refresh (#2899, milestone 299 step 1)

Since the scoped bucket (#2869) the ledger reads 100% accounted while 439
derive rows stand; the standing block was gated on unclassified > 0 and so
went silent. Build it whatever the todo count ("; standing: ..."), and add
derive_new — derive-grouped rows first seen after the previous refresh
stamp — so entering a project names the drift ("+2 new copies since last
refresh: .error-msg in InceptionCard.vue") instead of waiting for an audit.

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

src/scribe/mcp/tools/shapes.py

@@ -295,7 +295,9 @@ async def refresh_pattern_coverage(project_id: int) -> dict:
     Returns the accounting payload — total, accounted, counts by status,
     unclassified, repos, largest_gaps, `proposed` (canon proposals awaiting
     confirmation), `derive_groups` (the biggest repeats-with-no-canon
-    families), `proposer` (what this refresh examined) — plus
+    families), `derive_new` (copies that joined a family since the previous
+    refresh — the drift to act on now: derive the canon, don't queue an
+    audit), `proposer` (what this refresh examined) — plus
     `pattern_coverage`, the same one-line summary enter_project carries.
     """
     uid = current_user_id()