Make core growth visible: per-release size history, import-breadth bound, function-level layer guard #384

python-hwpx grew from 36,244 lines (5.0.1) to 78,053 (6.7.0), and `import hwpx` went from 70 to 117 hwpx modules. Nothing in the repository records this, so growth is only noticed by accident.

A layer audit also found application policy hidden inside core-owned files, which the path-based ownership ledger cannot see: Korean official-document reference rules in `tools/doc_diff.py`, a form-specific caption clean-up in `table_patch.py`, report-style heading guesses in `tools/markdown_export.py`, and core reading the automation layer's document-plan schema (`sections`/`blocks`).

Proposal:

• `docs/size-history.json`: lines per package, import breadth, and import time recorded once per release (release runbook step), not gated per PR.
• `tests/data/import_breadth.json`: an upper bound on the hwpx modules `import hwpx` loads; more fails, fewer passes.
• A function-level guard: Hangul regex literals and plan-schema keys in core product modules must be allowlisted with a reason. The existing hits are classified as format vocabulary or as known leaks scheduled to move in 7.0.