bench(learn): harvest signals for the decision engine (decision-engine task 5)

`ousast plane harvest` (plane/harvest.py) writes two Runs over a label snapshot:
verify a/b + agree on the verify-family units (both sides of each labelled pair as
an opaque files-only Workspace, candidates outside the hunt's root, no declared
sites; v1 and dev-php pins with repo-facts first) and model roles on the candidate
files (pair excerpts grouped, one Task per population pin). Budgets sum under the
ceiling by construction. New roles task template; the generator re-pins it.

Spent by attribution: verify $2.54 (1961 calls, 150 units, 182 hunts per pass),
roles $1.40 (1034 calls, 799 files, 0 unclassified chunks); DeepSeek balance
19.63 -> 18.23. Engine on the pair corpus (benchmarks/learn/engine_pairs.py,
frozen e6ed785, one 3g container) is PARTIAL: 384 of 686 sides at commit, still
running; unfinished sides stay missing. benchmarks/learn/build_features.py built
1712 static+plane records into the memory store; counts-only record under
benchmarks/measurements/2026-10-01-decision-engine-harvest/.

source/roles parts are `none`, not `failed`, for a language without a declaration
pattern (C). ops/ax/README: Substrate golden-actor disk leak and the inline
Workspace limit (~20 KB).

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01EmM1j46qgKMh3zqD1QMwEo

tests/test_learn_roles.py

@@ -156,6 +156,18 @@ def test_roles_feature_part(tmp_path: Path) -> None:
     assert [f.name for f in functions_of("a.php", lines, "php")][:2] == ["run_sql", "fetch_rows"]
 
 
+def test_a_language_without_declarations_is_none_not_failed() -> None:
+    """C has no declaration pattern: the span and wrapper roles cannot run there (no coverage), which is not a broken
+    instrument (harvest 2026-10-01: every memory pair read as `failed`)."""
+    from openultrasast.learn.features import source_part
+    from openultrasast.learn.roles import RoleSet
+
+    lines = ["int f(char *s) {", "  return strcpy(buf, s);", "}"]
+    assert source_part(lines, "c", "f").state == "none"
+    assert roles_part(None, RoleSet(sources=("inferred_wrapper",)), "c").state == "none"
+    assert source_part(["def g():", "    pass"], "python", "missing").state == "failed"
+
+
 def test_build_for_scan_records_the_roles_instrument(tmp_path: Path) -> None:
     from openultrasast.findings import quick_scan_findings
     from openultrasast.preprocess import preprocess_repository