fix: INSERT Form B value-count UX (ADR-0033 Amendment 5)

Three layered fixes for advanced/simple-mode positional INSERT
value-count mismatches (e.g. `insert into T values (...)` with the
wrong number of values for T's column count), plus ADR-0033
Amendment 5 recording the gate refinement.

Walker diagnostic (dml_insert_arity_diagnostics): the function's own
doc-comment recorded the no-column-list (Form B) case as deferred.
This commit closes that gap. Form B mismatches now emit a new
diagnostic.insert_arity_mismatch_form_b ERROR per offending tuple,
keyed off the target table's column count from the schema cache. The
[ERR] validity indicator (ADR-0027) lights up at typing time for the
reported scenario, no longer needing a submit.

Cross-mode pointer gate (advanced_alternative_note): refactored from
a hand-rolled Form B count check to a single input_verdict_in_mode(
input, schema, Mode::Advanced) call. The pointer fires only when the
verdict is None — the ADR-0027 sense of "valid". Any future static
check added to the verdict pipeline participates automatically; no
per-feature maintenance.

Teaching notes for the value-count cases users can hit before the
indicator turns red:
  - simple-mode submit: insert.form_b_extra_values_note covers under-,
    in-window, and over-supply against the Form B contract; suppressed
    when the cross-mode pointer fires (to avoid parallel advice).
  - advanced-mode dispatch pre-flight:
    insert.form_b_positional_count_mismatch_note catches a submitted
    mismatch with a teaching message before the engine produces its
    raw NOT-NULL / type error.

The advanced_mode.also_valid_sql pointer wording was reworked to
"trying to write SQL? switch with `mode advanced`, or prefix `:` to
run once". One insta snapshot regenerated.

ADR-0033 Amendment 5 records the gate change: Amendment 3's "would
parse in advanced mode" now reads as "valid in advanced mode" in the
explicit verdict-is-None sense, with the precise definition spelled
out so future readers can't drift back to the syntactic-only reading.
ADR-0000 index entry updated; docs/requirements.md H1a citation added
listing the three new pedagogical strings.

Tests added (8): four walker arity tests (under-supply, over-supply,
match, unknown-table); two app-level teaching-note tests for the
sibling cases (under-supply, over-supply beyond total); one pointer-
gate unit test pinning the bug-case suppression; one gate-precedence
test ensuring only one advice line per error. Existing
simple_mode_submit_of_sql_construct_appends_advanced_pointer updated
to use a known schema (the new validity gate requires it).

Full suite: 2031 passed, 0 failed, 0 unexpected skips. Clippy clean.

src/friendly/keys.rs

@@ -45,6 +45,12 @@ pub const KEYS_AND_PLACEHOLDERS: &[(&str, &[&str])] = &[
     ("diagnostic.duplicate_cte", &["name"]),
     ("diagnostic.eq_null", &[]),
     ("diagnostic.insert_arity_mismatch", &["expected", "actual"]),
+    // ADR-0033 §8.1 / Amendment 5: Form B (no column list) variant.
+    // Cited from issue #1 — every column must be supplied positionally.
+    (
+        "diagnostic.insert_arity_mismatch_form_b",
+        &["expected", "actual"],
+    ),
     ("diagnostic.not_null_missing", &["column"]),
     ("diagnostic.like_numeric", &["column", "type"]),
     ("diagnostic.projection_alias_misplaced", &["alias", "clause"]),
@@ -339,6 +345,20 @@ pub const KEYS_AND_PLACEHOLDERS: &[(&str, &[&str])] = &[
     // ---- Advanced-mode SQL surface (ADR-0030) ----
     ("advanced_mode.sql_in_simple", &["command"]),
     ("advanced_mode.also_valid_sql", &[]),
+    // Education note appended to a simple-mode INSERT Form B
+    // parse error when the user supplied more values than the
+    // non-auto-generated columns expect (issue #1 sub-task 2).
+    (
+        "insert.form_b_extra_values_note",
+        &["table", "expected_phrase", "auto_phrase", "all_cols"],
+    ),
+    // Pre-flight teaching note for advanced-mode positional
+    // `INSERT INTO T VALUES (…)` (no column list) when the value
+    // count doesn't match the column count (issue #1 sub-task 3).
+    (
+        "insert.form_b_positional_count_mismatch_note",
+        &["table", "col_count", "col_list", "supplied", "non_auto_csv"],
+    ),
     ("select.internal_table", &["table"]),
     (
         "cli.invalid_value",