grammar+db: 3i — auto_column_overridden diagnostic (ADR-0033 §8.2)

New dml_auto_column_diagnostics pass: a WARNING when a SQL INSERT's
explicit column list names a serial/shortid (auto-generated) column —
the explicit value bypasses the auto-counter/generator and may collide
with later auto-generated values. Advisory only (ADR-0027 §1); the
statement still runs. Conflict-target columns (distinct
conflict_target_column role) are not mistaken for inserted columns.

Catalog key diagnostic.auto_column_overridden (engine-neutral).
Tests (+4): serial + shortid fire; omitted is silent; ON CONFLICT
target not falsely flagged. 1580 pass / 0 fail / 1 ignored. Clippy
clean. Remaining 3i: insert_arity_mismatch, not_null_missing (needs
TableColumn not_null+default), cross-cut verification, #12 UPSERT
DO UPDATE validation.

src/friendly/keys.rs

@@ -39,6 +39,7 @@
 pub const KEYS_AND_PLACEHOLDERS: &[(&str, &[&str])] = &[
     // ---- Pre-submit diagnostics (ADR-0027) ----
     ("diagnostic.ambiguous_column", &["column", "qualifiers"]),
+    ("diagnostic.auto_column_overridden", &["column", "type"]),
     ("diagnostic.compound_arity_mismatch", &["op", "left_n", "right_n"]),
     ("diagnostic.cte_arity_mismatch", &["cte", "declared", "actual"]),
     ("diagnostic.duplicate_cte", &["name"]),