feat(contributor-scan): name the function a question cannot locate (M1b 12.3)

After per-family context, every remaining unresolved question reported
context_scope_empty, all in three files. The cause is not a missing producer:
app/routes/index.js requires seven handler modules and defines none of them, so a
question naming handleContributionsUpdate there names a function that file
genuinely does not hold, and the empty scope is the correct answer.

Reporting that as "scope empty" hid which of two different things had happened. A
file the frontend produced no methods for is one problem; a question naming a
function defined in another module is another, and it is the common one. Taint and
configuration now separate them, reporting context_function_unresolved with the
name in the first case and context_scope_empty only when the file has no methods at
all. The driver no longer stacks its generic gap on top of a query that already
explained itself, and the new gap is question-owned so it cannot block another
question's comparison.

Completion is deliberately unchanged. The tempting fix is to widen such a question
to its whole file, which would raise the number by answering a question nobody
asked; a question whose function the graph does not hold stays unresolved, with the
name now recoverable from the question that asked it.

Group 12 is complete: admission no longer rejects genuine findings on a
mis-extracted operation symbol, both families that could never complete their change
context now can, and the remaining unresolved questions say precisely why.

1,406 tests passed, nine skipped.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01EmM1j46qgKMh3zqD1QMwEo

tests/test_model_change_context.py

@@ -328,3 +328,22 @@ def test_a_family_whose_context_query_answers_nothing_stays_unresolved(tmp_path)
     outcomes = {o.identity.family: o for o in result.question_outcomes}
     assert "access_control" in outcomes
     assert any("context_projection_unavailable" in gap for gap in result.scope.unresolved_boundaries)
+
+
+def test_a_question_naming_a_function_the_file_does_not_define_says_so(tmp_path):
+    """M1b 12.3: a route-registration file names handlers defined elsewhere; that is not an empty file."""
+    from dataclasses import replace as _replace
+
+    (tmp_path / "source.js").write_text("readable\n")
+    boundary = {"kind": "context_boundary", "reason": "context_function_unresolved:contributor-scan", "function": "handleUpdate"}
+    unresolved = [{"kind": "context_summary"}, boundary]
+    backend = FamilyBackend({"source.js": vector() + unresolved}, {"dominance": [], "config": unresolved})
+    target = _replace(region("source.js", "javascript"), function="handleUpdate", families=("injection",))
+    result = scan_repository(tmp_path, [target], backend=backend, change_context=context("source.js"), population_complete=True)
+    outcome = result.question_outcomes[0]
+    assert outcome.status == "unresolved" and outcome.reason == "change_context_incomplete"
+    gaps = [g for g in result.scope.unresolved_boundaries if "context_function_unresolved" in g]
+    assert gaps, "the unresolvable function must be named, not reported as an empty scope"
+    # The gap is owned by the question that asked it, so it cannot block another question.
+    assert gaps[0].endswith(outcome.identity.question_id)
+    assert not any("context_scope_empty" in g for g in result.scope.unresolved_boundaries)