feat(ledger): mechanical proposer — every refresh proposes instances against canon and groups derive-first candidates; agents confirm in batches (#2792, milestone 294 step 6)

Shapes now carry a content fingerprint (signature + whitespace/comment-
insensitive body_sha; migration 0080) and the proposer runs inside the
coverage refresh, the one moment bodies exist: symbol elsewhere → textual
containment → body references the canon → signature resemblance → semantic
(capped per refresh, unreached rows stay unexamined for the next). A hit is
a proposal on the row (proposed_snippet_id/basis/score), never a
classification; rows with no canon hit group by the derive-first rule
(identical body in ≥2 places, same name in ≥3 files) as proposal_basis=
derive + a group key. list_shapes(proposal=any|canon|derive|<basis>) is the
queue; confirm_shape_proposals(project_id, snippet_id|path|basis) confirms
in batches as agent instances; any classify_shapes/hook stamp retires the
proposal. Readout carries proposed + derive_groups (line, payload, card).
Plugin 0.1.35 (skill: the machine proposes, judgment classifies).

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

tests/test_pattern_coverage.py

@@ -456,3 +456,54 @@ async def test_unservable_binding_measures_nothing(seeded):
     await set_binding(uid, "https://github.com/somebody/else.git", other_pid)
 
     assert await compute_coverage(uid, other_pid, selector=_selector(_tarball(TREE))) is None
+
+
+# --- #2792: fingerprints and the proposer's readout --------------------------
+
+
+def test_extract_definitions_fingerprints_each_block():
+    """The block rule across the language families the extractor knows: a
+    Python def ends at the next top-level statement, a braces/CSS block keeps
+    its closer, and comments/decorators don't move the hash."""
+    from scribe.services.coverage import extract_definitions
+
+    text = (
+        "import os\n\n"
+        "def a(x):\n    # comment\n    return x + 1\n\n\n"
+        "class B:\n    def m(self):\n        return 2\n\n"
+        ".btn {\n  color: red;\n}\n"
+        "export const f = (x) => {\n  return x;\n};\n"
+    )
+    defs = {d.name: d for d in extract_definitions(text)}
+    assert set(defs) == {"a", "B", "m", "btn", "f"}
+    assert defs["a"].signature == "def a(x):"
+    assert defs["a"].body.startswith("def a(x):\n    # comment\n    return x + 1")
+    assert "class B" not in defs["a"].body
+    assert defs["B"].body.rstrip().endswith("return 2")
+    assert defs["btn"].body == ".btn {\n  color: red;\n}"
+    assert defs["f"].body == "export const f = (x) => {\n  return x;\n};"
+    assert all(len(d.body_sha) == 16 for d in defs.values())
+    # Comment changes don't change what the shape IS; code changes do.
+    again = {d.name: d for d in extract_definitions(text.replace("# comment", "# other"))}
+    assert again["a"].body_sha == defs["a"].body_sha
+    changed = {d.name: d for d in extract_definitions(text.replace("x + 1", "x + 2"))}
+    assert changed["a"].body_sha != defs["a"].body_sha
+    # And the identity view is unchanged for the hook mirror.
+    from scribe.services.coverage import extract_shapes
+    assert extract_shapes(text) == [(d.kind, d.name) for d in extract_definitions(text)]
+
+
+def test_coverage_line_names_the_proposers_standing():
+    from scribe.services.coverage import coverage_line
+
+    base = {
+        "total": 100, "accounted": 10, "unclassified": 90,
+        "counts": {"canonical": 10, "instance": 0, "variant": 0, "exempt": 0},
+        "computed_at": "2026-08-21T00:00:00+00:00",
+        "largest_gaps": [{"dir": "src", "unclassified": 90, "total": 90}],
+    }
+    assert coverage_line(base).endswith("; 90 unclassified, largest: src")
+    line = coverage_line({**base, "proposed": 40, "derive_groups": [{"group": "a"}, {"group": "b"}]})
+    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