T4-W05 Existing Data Compatibility

Verdict: EXISTING_DATA_COMPATIBILITY_PROVEN

Change	Impact
Faculty save sheet↔session bind	Behavioral only; existing sheets unaffected
Batch membership check on save	Rejects new invalid writes; historical lines retained
Elevated line create for teachers	Fixes ACL create=0 gap; no schema change
_line_status Sakit detection	Read-label improvement via leave_type/remark
Parent proof_file stripped	Response minimization; DB proofs retained
Student own-line ir.rule	Restricts RPC search; portal API unchanged
get_student_for_user elevation	Identity resolve only

No uniqueness constraint added beyond existing OpenEduCat SQL uniques. No forced migration of historical attendance rows.