Extract catalog generated-surface ownership

[Anionix]

Closes #5
Part of #2

Summary

• Added scripts/catalog_surface.py as the lower generated-surface ownership module for slugging, paper-note expectations, obsolete note detection, tracked-file discovery, manifest planning, output planning/comparison, and generated view freshness.
• Kept scripts/generate_catalog.py as the command adapter for writing generated files.
• Updated scripts/validate_catalog.py to use catalog_surface for expected outputs and freshness checks instead of importing the generator command adapter.
• Left SQL corpus behavior unchanged; scripts/sql_corpus.py has no diff.

Generated diff

• Ran make generate; the only generated repository-surface diff was the deterministic manifest.json file-list addition for scripts/catalog_surface.py.

Validation

• make generate passed.
• PYTHONDONTWRITEBYTECODE=1 make check passed: catalog validation passed, generated check passed, SQL static check passed.
• PYTHONDONTWRITEBYTECODE=1 make sql-check passed: SQL static check passed; DATABASE_URL was unset, so live PostgreSQL execution was skipped after static SQL checks.
• git diff --check passed.
• Extra: git diff --cached --check passed before commit.