fix(scan): scope a partition census gap to its own partition, and write the rule down

A missing JavaScript file cannot make a PHP answer wrong. A census gap now carries the partition it
was raised for, and reaches only that partition questions. On the measured plugin four JavaScript
files -- a webpack build output, a minified select2, a build config and one source file -- had taken
the admissibility of 4,425 PHP regions with them.

Two controls exercise the real boundaries rather than injecting a reason, and both were confirmed to
FAIL with the old classification restored, so they guard what they claim to.

And the rule is now in the design, because this was the fifth instance found and fixed one at a time.
Two invariants, eleven instances between them:

  A degradation is owned by the narrowest scope that caused it. Vendor exclusion as a global veto,
  line ambiguity inherited by every question, an empty scope blocking a sibling comparison, a language
  boundary demoting every answer, a census gap demoting every answer. The fourth and fifth cost the
  declared v0.1 target its entire admissibility, and neither passing subject could reveal it because
  both hold one language.

  A token matches the thing it names, not text that contains it. gets inside fgets, resolve inside
  resolveUrl, user inside users, a sink word inside a comment, a dotted setting on its last segment,
  a flow query reading the receiver.

Each carries a review test: a new degradation must state the scope it reaches and justify demoting
that far, and a text match must be bounded AND confined to the part of the node that names the callee.

1,419 tests pass, eighteen skipped.

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

.kiro/specs/pre-push-safety-net/tasks.md

@@ -568,6 +568,8 @@ Preserve all completed task evidence below.
   - Recording the boundary is right: a flow from PHP into JavaScript is semantics the partitioned graph cannot follow. Demoting every question is not, including one wholly inside a single PHP file. Task 12.3 already fixed this bug class one level down, making an empty-scope gap question-owned "so it cannot block another question's comparison"; the same principle applies to a partition boundary.
   - Do not reclassify the reason as a declared exclusion. That would claim cross-language flows are out of scope when they are unresolved, which is the opposite of what this project's degradation vocabulary exists to say.
   - Done when a question whose scope lies inside one partition completes, a question whose scope could cross a partition boundary stays unresolved with the boundary named, and no question completes by widening its scope. Evidence: `benchmarks/measurements/2026-09-21-two-languages-defeat-completion.json`.
+  - _Both halves implemented 2026-09-21._ A language boundary is now a declared limit: it can hide a finding and never invent one, so it stays published and stops demoting. And an integrity gap raised by a partition census now carries the partition it came from and reaches only that partition's questions, because a missing JavaScript file cannot make a PHP answer wrong. Two controls exercise the real boundaries rather than injecting a reason, and both were confirmed to FAIL with the classification restored. The rule behind both is now written in the design as an invariant, with all five instances listed, because this is the fifth time it has been found and fixed one instance at a time.
+  - _Not yet verified on a subject._ PMPro is the measurement that motivated this and it must be re-run to show a PHP question completing. That run is what closes this task.
   - _Boundary: contributor-scan query/context evidence, Ranker Scope Contract_
   - _Depends: 13.3_
   - _Requirements: 2.1, 2.2, 6.3, 8.1_