docs: mark H1a done via the ADR-0042 systematic pass

requirements.md H1a → [x]: the per-command near-miss matrix (entry words,
missing clauses, committed multi-forms, both modes) plus the gap fixes
(G1 `1:n relationship`, G2 select projection gloss, G3 mode-aware usage
showing all valid forms, G4 `with` CTE template, CROSS JOIN ON teaching
message) close the systematic pass. The advanced-SQL items the survey
flagged (INSERT…SELECT count, RETURNING scope) were verified already
present. One low-priority residual is deferred by decision (submit-time
expression first-set at non-projection positions).

ADR-0042: record the pre-existing `SELECT *` arity caveat (INSERT…SELECT
with a star projection isn't expanded for pre-flight arity; engine
catches it at execution — adjacent to ADR-0019 §OOS-2).

docs/adr/0042-h1a-parse-error-pedagogy-grammar-tree.md

@@ -266,7 +266,13 @@ Verifying each against the running app **reversed two of three**:
 - **INSERT…SELECT column-count** is *already handled* — a count
   mismatch fires `verdict = Error` with "the column list names N
   column(s) but M value(s) are given" (walker test
-  `insert_select_arity_mismatch_fires`). Not a gap.
+  `insert_select_arity_mismatch_fires`). It is a structural
+  list-vs-list check, so it fires even without a schema. Not a gap.
+  *Caveat (pre-existing, not addressed here):* a `SELECT *`
+  projection is not expanded for arity, so `insert into T (one_col)
+  select * from Multi` is not pre-caught — the engine rejects it at
+  execution. Star-expansion for pre-flight arity would be a separate
+  enhancement (and brushes ADR-0019 §OOS-2 engine-error territory).
 - **RETURNING scope** is *already handled* — at a bare `returning`
   position completion offers the table's columns; `returning
   <unknown>` fires the `unknown_column` diagnostic. Not a gap.

docs/requirements.md

@@ -557,14 +557,14 @@ since ADR-0027.)
   migration sweep of all other user-facing strings, advanced-mode
   SQL-error sanitization (§OOS-2), and `messages` persistence
   (§OOS-3, awaits the settings ADR).)*
-- [ ] **H1a** Strong syntax-help in parse errors. When the user
+- [x] **H1a** Strong syntax-help in parse errors. When the user
   types something near-correct (e.g. `insert into T ('Oli')` —
   forgotten `values`; or `update T set x=1` — missing WHERE),
   the error should *name the missing keyword or clause* rather
   than just point at the unexpected character. This is a
   separate effort from H1 (which targets database errors); it
-  targets parser errors. Pending — multiple targeted fixes
+  targets parser errors. *(Done via the **ADR-0042** systematic
-  shipping piecemeal so far (e.g. `values` becoming optional in
+  pass, 2026-06-06.)* Built piecemeal first (e.g. `values` becoming optional in
   INSERT removes one such case; ADR-0024's typed value slots
   give per-column-type rejection wording; `insert into T (col)`
   with no `values` clause now flags "looks like Form A — add
@@ -589,8 +589,23 @@ since ADR-0027.)
   `col`…"* message at typing time, counted against the user-fillable
   columns, with `serial`/`shortid` auto-fill named; new keys
   `diagnostic.insert_arity_mismatch_form_b_simple` /
-  `diagnostic.insert_arity_mismatch_all_auto`). A systematic pass is
+  `diagnostic.insert_arity_mismatch_all_auto`). The **ADR-0042
-  still pending.
+  systematic pass** then closed it: a per-command near-miss matrix
+  (`tests/it/parse_error_pedagogy.rs`) locks every entry word's
+  bare / missing-clause / wrong-token cases plus the committed
+  multi-forms, in both modes; friendlier labels landed (`add` →
+  `1:n relationship`; bare `select` → "a projection: …"); the
+  usage block became mode-aware (advanced shows the SQL forms
+  plus the still-valid DSL fallback forms, SQL-first); `with`
+  got its own CTE template; and `cross join … on` now teaches
+  that a CROSS JOIN takes no ON clause. The advanced-SQL
+  diagnostics that the survey thought missing (INSERT…SELECT
+  count, RETURNING column scope) were verified already present.
+  One low-priority residual is deferred by decision: at *submit*
+  time a non-projection expression position (bare `where `,
+  `returning `) still shows the raw expression first-set —
+  typing-time completion already offers the right candidates
+  there, so the payoff is small.
 - [ ] **H2** `hint` provides contextual help for the current
   input or the most recent error.
 - [ ] **H3** `help` provides general reference and per-command