fix(quality): record the 2026-09-02 merged growth in the file-size baseline (#12434)

check-file-size was red on release/v3.8.51 with nine violations — seven source files and two test files that the 2026-09-02 merge waves grew at existing chokepoints (#12359-#12404, #11461, #11513, #12423).

The growth itself was reviewed: each file was measured and justified while validating those batches. What went wrong is the propagation — the rebaseline was computed in the throwaway combined validation worktree, and the PRs were then merged individually through their own branches, so the code landed and the caps did not. A shared-file edit made only in the validation tree reaches nothing.

This records the caps against the merged state, each entry attributed to the PR that grew it, under one _rebaseline annotation. Verified mechanically: 9 caps recorded, 0 raised beyond the file's real merged LOC, 0 unrelated entries moved — the ratchet #12411 re-tightened is intact.

Verified: check-file-size OK (135 frozen source entries across 4515 files; 39 frozen test entries across 5365), prettier clean.