fix: insert VALUES between-values hint points at comma not close-paren

The ambient-hint fallback in ambient_hint_core_in_mode parsed
schemalessly, so the type-blind grammar closed an `insert … values
(…)` tuple after the first value and the "Next:" hint pointed at `)`.
With a schema available the walk knows the remaining columns and the
correct next token is `,`. Parse the fallback with the schema cache so
the expected-token prose matches the rest of the (already
schema-aware) hint ladder.

Also corrects wrong-arity closed tuples where the schemaless parse
accepted the input and the hint said "submit with Enter" for a command
the schema-aware parse rejects — the hint now surfaces the accurate
error. Three typing-surface snapshots updated to match.

Docs: ADR-0022 Amendment 3 (+ README index) records the schema-aware
fallback; requirements.md H1a cites the hint-accuracy improvement.

docs/requirements.md

@@ -535,7 +535,15 @@ handoff-14 cleanup; 449 after B2/C2.)
   value-count class (`insert.form_b_positional_count_mismatch_note`),
   plus a walker-level `diagnostic.insert_arity_mismatch_form_b`
   ERROR that lights the `[ERR]` validity indicator at typing
-  time). A systematic pass is still pending.
+  time; **issue #2 / ADR-0022 Amendment 3, 2026-05-29** made the
+  ambient-hint fallback rung schema-aware so the "Next:" prose
+  names the schema-correct next token (`,` between values, `)`
+  after the last) instead of the type-blind close-paren, and so a
+  wrong-arity closed tuple surfaces the real parse error rather
+  than a misleading "submit with Enter"). A systematic pass is
+  still pending; simple-mode wrong-count tuples still get a generic
+  expected-token message rather than the friendly arity diagnostic
+  advanced mode shows (issue #17).
 - [ ] **H2** `hint` provides contextual help for the current
   input or the most recent error.
 - [ ] **H3** `help` provides general reference and per-command