fix: invalidate empty-table proof after writes and table renames

DECISIONS.md

@@ -4,9 +4,12 @@
 
 **Decision.** The `NOT_NULL` SQL check accepts `ALTER TABLE ... ADD COLUMN ... NOT NULL`
 only when the same migration unconditionally created that exact table. `CREATE TABLE IF
-NOT EXISTS` does not prove an empty table. The migration remains
-fully linted, so `RunSQL`, `RunPython`, and operations on existing tables retain their
-checks.
+NOT EXISTS`, SQL inserts, and data operations, including nested
+`SeparateDatabaseAndState` operations, do not prove an empty table. The migration remains fully
+linted, so top-level and nested `RunSQL` and `RunPython`, and operations on existing tables retain
+their checks. Custom database operations are not trusted as declarative schema operations and
+therefore invalidate the proof. Table renames also invalidate it because a name can be reused by a
+populated table.
 
 **Rejected.** Ignoring all initial migrations or naming them as exemptions. Either option
 skips unsafe operations that the linter must inspect.