Add table-level CHECK (e.g. `CREATE TABLE t (a int, b int, CHECK (a < b))`)
to advanced-mode SQL CREATE TABLE. Since SQLite exposes no PRAGMA for CHECK
constraints, a table-level CHECK cannot be read back from the engine and
becomes the source of truth in a new internal metadata table
`__rdbms_playground_table_checks (table_name, seq, check_expr)`.
- Grammar: new TABLE_CHECK element in ELEMENT_CHOICES.
- Builder: distinguishes a table-level CHECK from a column-level one by
element position (no column-def open in the element), using depth-aware
boundary tracking so a length-arg comma (`numeric(10,2)`) or a
table-PRIMARY KEY's inner comma is not mistaken for an element separator.
- Worker: do_create_table emits the CHECK clauses and writes the metadata
rows in its transaction; schema_to_ddl emits them identically on rebuild;
read_schema / read_schema_snapshot read them from the metadata table;
do_drop_table clears them.
- Persistence: TableSchema.check_constraints round-trips through project.yaml
(#[serde(default)], optional on read), mirroring unique_constraints.
- Composite UNIQUE deliberately stays PRAGMA-detected (engine-reportable,
unlike CHECK) — user-confirmed.
DA/runda round added cross-cutting tests and a forward-looking doc fix:
- table CHECK survives a rebuild triggered by `add column`, and a later
rebuild_from_text (the ADR-0013 rebuild primitive uses a raw DROP, so the
metadata rows keyed on the final name are preserved);
- dropping a column a table CHECK references fails cleanly (rollback, table
intact); detection is 4e, friendly wording is H1;
- dropping a table clears its CHECK metadata (no orphan rows on re-create);
- amended ADR §6 so 4h's RENAME also updates the new metadata table.
20 Tier-3 + 9 grammar/builder + 2 YAML tests. Docs: ADR-0035 Status/§13/§6,
README index, requirements.md Q1. Help/usage skeleton + describe display of
table-level constraints deferred to 4i (symmetric with 4a.2).
Tests: 1769 passing, 0 failing, 1 ignored. Clippy clean.