feat(ledger): classify_shapes + list_shapes MCP tools; get_snippet carries the consumer map (#2789, milestone 294 step 3)

The judgment write path. classify_shapes applies a batch of classifications
to a project's live ledger rows — all-or-nothing (#2709's lesson: the whole
batch is validated, write-ACL'd, and every snippet target proven readable
before any row is touched); rows match by exact (path, symbol), kind narrows,
and shapes no live row matches come back as 'unmatched' rather than errors.
variant/exempt REQUIRE the reason — the why is the record (note 2786) — and
'unclassified' deliberately withdraws a judgment back to the todo. The 'via'
channel is caller-restricted to agent|audit|import; hook and mechanical stay
server-internal so a caller can't launder judgment as machinery.

list_shapes is the todo query (status=unclassified) with composable filters:
path is exact-or-under like recorded locations, snippet_id reads a consumer
map, include_vanished reads history; paged with the true total.

get_snippet now attaches  and  — the structured consumer
map, filtered to projects the CALLER can read so a shared snippet never side-
channels another project's file layout; attached only when non-empty (#2483).

Integration tests pin the batch atomicity, ACL gates, filter composition, the
consumer map on the MCP pull, and the SET NULL companion: a judgment whose
snippet was purged rejoins the todo on the next sync.

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

tests/test_shape_ledger.py

@@ -50,3 +50,35 @@ def test_status_queries_have_an_index():
     names = {ix.name for ix in CodeShape.__table__.indexes}
     assert "ix_code_shapes_project_status" in names
     assert "ix_code_shapes_snippet" in names
+
+
+# --- step 3: the classification batch validator (pure, checked before ACL) ---
+
+
+def test_batch_validation_names_the_failing_item():
+    from scribe.services.shape_ledger import validate_classifications as v
+
+    ok = {"path": "src/a.py", "symbol": "f", "status": "exempt", "reason": "one-off"}
+    assert v([ok]) is None
+    assert "empty" in v([])
+    assert "classifications[1]" in v([ok, {"symbol": "f", "status": "exempt"}])
+    assert "unknown status" in v([{**ok, "status": "covered"}])
+    # A judgment that references canon must name the canon...
+    assert "needs snippet_id" in v(
+        [{"path": "a", "symbol": "f", "status": "instance"}]
+    )
+    # ...and a departure/exemption must carry its why — the why IS the record.
+    assert "needs a reason" in v(
+        [{"path": "a", "symbol": "f", "status": "variant", "snippet_id": 3}]
+    )
+    assert "needs a reason" in v([{"path": "a", "symbol": "f", "status": "exempt"}])
+    # Withdrawing a judgment needs neither target nor reason.
+    assert v([{"path": "a", "symbol": "f", "status": "unclassified"}]) is None
+
+
+def test_classify_and_list_are_mounted_as_mcp_tools():
+    from scribe.mcp.server import build_mcp_server
+
+    mcp = build_mcp_server()
+    for name in ("classify_shapes", "list_shapes"):
+        assert mcp._tool_manager.get_tool(name) is not None