feat: ADR-0035 4a — SQL CREATE TABLE command, worker, and exit gate

Command + builder + worker for advanced-mode SQL CREATE TABLE
(sub-phase 4a), executed structurally through do_create_table:

- Command::SqlCreateTable + build_sql_create_table (ddl.rs): aliases via
  from_sql_name (incl. double precision), column- and table-level
  PRIMARY KEY, redundant-flag de-dup off a sole PK, IF NOT EXISTS.
  Advanced REGISTRY entry on the shared `create` word (SQL-first, DSL
  fallback); no-PK tables allowed (user-confirmed).
- Worker (db.rs): Request::SqlCreateTable + CreateOutcome + snapshot_then
  (one undo step); IF NOT EXISTS no-op (no snapshot, but journalled, like
  read-only commands). do_create_table inline-PK rule aligned with the
  rebuild generator schema_to_ddl — no round-trip DDL drift; serial
  autoincrement is independent of inline-PK (verified by round-trip
  tests).
- Runtime/App: dispatch + CommandOutcome::SchemaSkipped +
  AppEvent::DslCreateSkipped (structure + "already exists — skipped"
  note). Friendly catalog keys added (engine-neutral).

DEFAULT/CHECK/table-level UNIQUE are absent from the 4a grammar (parse
error with usage skeleton; friendly message + support land in the 4a.2
constraint slice) — user-confirmed.

Tests: type resolver, grammar shape, builder (incl. the PK
detection bug they caught), and tests/sql_create_table.rs (worker
round-trip, serial autoincrement first/non-first across rebuild, IF NOT
EXISTS no-op + journalling, no-PK table, one undo step) + a replay-as-
write test. 1739 pass / 0 fail / 1 ignored; clippy clean.

Exit gate: ADR-0035 Proposed -> Accepted (validated end-to-end by 4a);
README + requirements.md Q1 updated.

docs/requirements.md

@@ -209,14 +209,17 @@ handoff-14 cleanup; 449 after B2/C2.)
 
 - [ ] **Q1** SQL parsed via `sqlparser-rs`; supported subset is
   defined (specifics deferred to a future ADR).
-  *(Progress: SQL handling in advanced mode is still a
-  placeholder echo. The architecture is now decided — ADR-0030:
-  SQL is authored as grammar within the unified grammar tree
-  (ADR-0024) and parsed by the existing walker, **not** a
-  separate batch parser — so SQL gets the same completion /
-  highlighting / hints as the DSL. ADR-0001's `sqlparser-rs`
-  reservation is superseded. Implementation is phased and
-  pending.)*
+  *(Progress: the advanced-mode SQL surface is authored as grammar
+  within the unified grammar tree (ADR-0030 / ADR-0024) and parsed by
+  the existing walker — **not** a separate batch parser — so SQL gets
+  the same completion / highlighting / hints as the DSL (ADR-0001's
+  `sqlparser-rs` reservation is superseded). Implemented so far: full
+  `SELECT` (ADR-0032), `INSERT` / `UPDATE` / `DELETE` (ADR-0033), and
+  `CREATE TABLE` (ADR-0035 sub-phase 4a, 2026-05-25 — columns + types +
+  `NOT NULL` / `UNIQUE` / `PRIMARY KEY` + `IF NOT EXISTS`, executed
+  structurally). Remaining DDL — `CREATE TABLE` constraints (4a.2),
+  FK (4b), `DROP TABLE` (4c), indexes (4d), `ALTER TABLE` (4e–4h) — is
+  phased per ADR-0035 §13.)*
 - [ ] **Q2** Non-standard syntax rejected with a clear message
   pointing at the supported subset.
   *(Design done — ADR-0030 §8: out-of-subset statements are