feat(pre-push-safety-net): export the enumerated operation inventory (M1b 10.4)

A taint answer reports traced flows, so an absent row means either that the
operation is not present or that no traced path reached it. Change comparison
needs that distinction to say a change introduced an operation, and reachability
is deliberately bounded, so the two can never be separated from flow rows alone.
That is why the veto guarding the confusion is permanently true on any real
Express application, and why it could be neither discharged nor safely removed.

The taint query now exports one row per operation it enumerated in scope, plus a
completion marker. The marker is what makes an empty inventory meaningful:
without it a scope that was never enumerated and a scope holding no such
operation are indistinguishable.

Comparison separates three outcomes on a changed line: the operation is present
in the base without a traced flow, which is a reachability statement and not
novelty; the operation is absent from an enumerated base, which establishes that
the change introduced it; or the base scope was never enumerated, which stays
explicitly unresolved. A malformed inventory row is not an empty inventory.

The arbiter now skips any row carrying a kind, so an inventory row cannot be
normalized into a flow with an empty source that names no attacker input.

Verified against the real engine on an authored two-revision JavaScript control:
the operation is enumerated on both sides, the base carries it with zero traced
flows, the zero-operation marker appears for an empty scope, and answers and
findings are unchanged. No new sink inference, alias resolver or second source
IR. 1,354 tests passed, nine skipped. Rollout stays NO-GO.

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

tests/test_push_policy.py

@@ -155,7 +155,7 @@ def test_changed_new_operation_in_comparable_existing_file():
     # map to, so a complete counterpart answer containing no such operation now establishes
     # absence. Before that repair this stayed unknown and no introduced flow could be seen.
     ctx = replace(context(), spans=(ChangedSpan("a.js", 4, 4, "head"),), line_correspondences=())
-    assert delta(scan(), scan(rows=[], findings=False), ctx).novelty == "new"
+    assert delta(scan(), scan(rows=inventory_rows(), findings=False), ctx).novelty == "new"
     assert delta(scan(), scan(line=6), ctx).novelty == "unknown"  # movement is not new
 
 
@@ -299,7 +299,7 @@ def changed_line_context(*, ambiguous=False, head_line=4):
 
 def test_operation_introduced_on_a_changed_line_is_new_against_a_complete_base():
     """M1b 10.1: absence is established over the counterpart answer, not over a line anchor."""
-    candidate = delta(scan(), scan(rows=[], findings=False), changed_line_context())
+    candidate = delta(scan(), scan(rows=inventory_rows(), findings=False), changed_line_context())
     assert (candidate.novelty, candidate.reason) == ("new", "operation_absent_from_comparable_base")
 
 
@@ -411,16 +411,65 @@ def test_repeated_unchanged_lines_do_not_invalidate_a_distinct_operation():
     """M1b 10.3: file-wide ambiguity is scoped to the operations whose anchor needs it."""
     ambiguous = "612e6a73:" + "ambiguous_line_correspondence"
     ctx = replace(changed_line_context(), unresolved_boundaries=(ambiguous,))
-    assert delta(scan(), scan(rows=[], findings=False), ctx).novelty == "new"
+    assert delta(scan(), scan(rows=inventory_rows(), findings=False), ctx).novelty == "new"
 
 
 def test_an_operation_needing_an_ambiguous_anchor_is_still_uncomparable():
     ambiguous = "612e6a73:" + "ambiguous_line_correspondence"
     ctx = replace(changed_line_context(ambiguous=True), unresolved_boundaries=(ambiguous,))
-    assert delta(scan(), scan(rows=[], findings=False), ctx).novelty == "unknown"
+    assert delta(scan(), scan(rows=inventory_rows(), findings=False), ctx).novelty == "unknown"
 
 
 def test_any_other_transaction_context_gap_still_blocks():
     ctx = replace(changed_line_context(), unresolved_boundaries=("snapshot:lfs_blob_unavailable",))
     candidate = delta(scan(), scan(rows=[], findings=False), ctx)
     assert (candidate.novelty, candidate.reason) == ("unknown", "change_context_unresolved")
+
+
+def inventory_rows(*operations, complete=True, path="a.js", line=4):
+    rows = [
+        {"kind": "operation_inventory", "inventory": op, "inventoryFile": path, "inventoryLine": line, "inventoryMethod": "handler"}
+        for op in operations
+    ]
+    return rows + ([{"kind": "operation_inventory_complete", "operations": len(rows)}] if complete else [])
+
+
+def test_an_operation_present_in_the_base_inventory_is_not_new():
+    """M1b 10.4: no traced flow is a reachability statement, not absence of the operation."""
+    base = scan(rows=inventory_rows("exec(cmd)"), findings=False)
+    candidate = delta(scan(), base, changed_line_context())
+    assert candidate.novelty == "unknown"
+    assert candidate.reason == "operation_present_in_base_without_traced_flow"
+
+
+def test_an_enumerated_base_without_the_operation_establishes_absence():
+    base = scan(rows=inventory_rows("query(sql, params)"), findings=False)
+    candidate = delta(scan(), base, changed_line_context())
+    assert (candidate.novelty, candidate.reason) == ("new", "operation_absent_from_comparable_base")
+
+
+def test_an_empty_but_enumerated_scope_establishes_absence():
+    base = scan(rows=inventory_rows(), findings=False)
+    assert delta(scan(), base, changed_line_context()).novelty == "new"
+
+
+def test_an_unenumerated_base_scope_stays_unresolved():
+    base = scan(rows=[], findings=False)
+    candidate = delta(scan(), base, changed_line_context())
+    assert candidate.novelty == "unknown"
+    assert candidate.reason == "base_operation_inventory_unavailable"
+
+
+def test_a_malformed_inventory_row_is_not_an_empty_inventory():
+    broken = [{"kind": "operation_inventory", "inventory": "exec(cmd)", "inventoryFile": "a.js", "inventoryLine": "0"}]
+    broken.append({"kind": "operation_inventory_complete", "operations": 1})
+    candidate = delta(scan(), scan(rows=broken, findings=False), changed_line_context())
+    assert candidate.reason == "base_operation_inventory_unavailable"
+
+
+def test_inventory_rows_do_not_count_as_unparsed_answer_body():
+    """A completed answer carrying an inventory is still a valid answer, not a malformed one."""
+    head = scan()
+    rows = json.loads(head.question_outcomes[0].raw_rows_json) + inventory_rows("exec(cmd)")
+    head = replace(head, question_outcomes=(replace(head.question_outcomes[0], raw_rows_json=json.dumps(rows)),))
+    assert delta(head, scan(rows=inventory_rows("query(sql, params)"), findings=False), changed_line_context()).novelty == "new"