fix(workbook): honor stable column IDs in structural edit guards

[rudycelekli]

Summary

Workbook formulas resolve exact column IDs before display names. The structural edit guards did not use that precedence: an unrelated column named source could block deletion or rename even when {source} referenced a different column whose ID was source.

This fix keeps exact stable ID references authoritative during deletion, rename and whole-config replacement. Real display-name dependencies and ambiguous aliases remain blocked, so an edit cannot silently redirect those references.

Verification

• Locked native backend suite: 2,220 passed, 134 skipped, five deselected under the existing CI selection.
• PostgreSQL 18 integrity/tenancy suite: 20 passed.
• Frontend lint/build and 63 tests passed; extension 16 tests passed.
• Mounted browser regressions: three passed.
• Real API/ORM causal proof: the original implementation produces three HTTP 409 failures for deletion, rename and replacement, while the genuine display-name dependency control passes. The candidate passes all four, retaining the referenced source column, formula and zero queued jobs.

Native fork validation: https://github.com/rudycelekli/OpenGTM/actions/runs/38406866232, source head 6ffa03b45a24c28eaa9c4c36d8ed393c6a1cc102.

Prepared with AI assistance and independently reviewed before publication. No live provider calls or production data were used for the regression fixtures.