create table: column constraints — NOT NULL / UNIQUE / DEFAULT grammar (ADR-0029)

`create table … with pk` now parses the column-constraint
suffix; combined with the commit-1 db layer, a constrained
table works end to end.

- A shared constraint-suffix grammar fragment — `not null`,
  `unique`, `default <literal>` — sits after each column's
  `(type)` group; `build_create_table` walks the matched path
  per column and folds the constraints into `ColumnSpec`.
- §9 redundancy check: every `with pk` column is a primary-key
  column, so `not null` (any) and `unique` (single-column PK)
  are rejected with a friendly error
  (`parse.custom.constraint_redundant_on_pk`).
- `project.yaml` round-trip: `ColumnSchema` gains `not_null` /
  `default`; the YAML reader/writer and `build_read_schema`
  carry them, so `rebuild` / `export` / `import` preserve
  constraints.
- ADR-0029 §2.1's example corrected — `create table` columns
  are all PK columns, so its suffix is for `default` / `check`;
  `docs/simple-mode-limitations.md` records that non-PK
  columns at create time need advanced mode.

CHECK is deferred to the next commit. 1184 tests pass (+7);
clippy clean.

docs/simple-mode-limitations.md

@@ -38,3 +38,13 @@ entry names the ADR that drew the boundary.
   yet available.
 - **No `LIMIT … OFFSET`** — `limit` takes a row count
   only.
+
+## Table creation (ADR-0029)
+
+- **`create table` declares only primary-key columns.**
+  `create table T with pk …` makes every listed column part
+  of the primary key; there is no simple-mode syntax for a
+  non-PK column in the same statement. Non-PK columns are
+  added afterward with `add column`. Creating a table with a
+  mix of PK and non-PK columns in one statement needs
+  advanced-mode `CREATE TABLE` syntax.