docs: ADR-0032 + Phase 2 plan — full SQL SELECT grammar

ADR-0030 §3 commissioned a focused ADR for the full SELECT
grammar (the "SELECT — full" phase). ADR-0032 records the
decisions; docs/plans/20260520-adr-0032-phase-2.md is the
implementation plan walking the work.

Phase 2's grammar surface:

- Five JOIN flavours (INNER, LEFT, RIGHT, FULL OUTER, CROSS).
  NATURAL/USING/comma-FROM explicitly OOS.
- All four set ops (UNION, UNION ALL, INTERSECT, EXCEPT).
- WITH and WITH RECURSIVE CTEs, with optional (col-list) renaming.
- Scalar subqueries, IN (SELECT …), [NOT] EXISTS as additive
  primary branches in sql_expr (redeems ADR-0031 §7 OOS-1).
- Qualified column refs t.c / alias.c as a name_or_call tail
  (redeems ADR-0031 §7 OOS-2).
- LIMIT n [OFFSET m]; legacy `LIMIT m, n` OOS.
- DISTINCT/ALL, t.* projection, bare-alias projection (lifts
  Phase-1 §4.2's autonomous decision).

Walker-capability honesty (§10): ADR-0030 §8's "ambient
assistance comes for free" holds for grammar recursion (reuses
ADR-0026's Subgrammar + depth cap unchanged) but not for
completion scope. Phase 2 adds a new Node::ScopedSubgrammar
variant alongside the existing Node::Subgrammar (DSL Expr and
sql_expr recursion untouched), a from_scope_stack of
ScopeFrames holding from_scope / cte_bindings /
projection_aliases, qualified-prefix completion narrowing, and
a post-walk fixup pass that re-resolves projection-list
identifier highlighting/validity once FROM is parsed (the
projection-before-FROM problem).

CTE column resolution (§10.3): SELECT * and explicit-projection
CTE bodies both yield real column completion past cte_alias.|
via a body-projection derivation rule that runs at the body's
ScopedSubgrammar exit and writes derived columns back into the
binding.

Diagnostics (§11): every Phase-2 validation case classified
against ADR-0027's ERROR/WARNING guideline. Five new diagnostic.*
catalog keys for parse-time-detectable cases (unknown_qualifier,
ambiguous_column, projection_alias_misplaced, cte_arity_mismatch,
compound_arity_mismatch) plus eight engine.* translation keys.
A MatchedPath-walking predicate-warnings variant closes the
Phase-1 carry-over gap where SQL WHERE expressions emitted no
LIKE-on-numeric / = NULL / type-mismatch warnings — ADR-0027
Amendment 1 finally extends to the SQL surface.

Result-column type resolution (§12): rusqlite 0.39.0 exposes
column_table_name / column_origin_name / column_database_name
behind a `column_metadata` feature; verified. Bare column refs
recover their playground type — partially lifts Phase-1 §4.5's
bool→0/1 deferral.

The implementation plan breaks Phase 2 into seven sub-phases
(2a–2g) with explicit exit gates per sub-phase and a cross-cut
verification matrix that names every "X comes for free" claim
from ADR-0030/0031/0032. The Phase-1 SQL-expression
predicate-warning gap is a named row, preventing an analogous
silent gap from shipping. The plan encodes the user's standing
authorization for the implementer to walk uninterrupted between
gates and commit with standard messages — escalation
discipline preserved for design ambiguities and real blockers.
Pushes remain user-only.

New docs/plans/ directory sets a pattern for future phase plans.

Status: Accepted.

docs/adr/README.md

@@ -37,3 +37,4 @@ This directory contains the project's ADRs, recorded per
 - [ADR-0029 — Column constraints (NOT NULL / UNIQUE / CHECK / DEFAULT)](0029-column-constraints.md) — **Accepted**, the four column-level constraints declared in the column-spec suffix (`create table` / `add column`) and modified on existing columns via `add constraint …` / `drop constraint …`; a pre-flight dry-run guards populated columns; `CHECK` reuses the ADR-0026 expression grammar via `Subgrammar` (`C3`)
 - [ADR-0030 — Advanced mode: the standard-SQL surface](0030-advanced-mode-sql-surface.md) — **Accepted**, SQL added as grammar *within the unified grammar tree* (ADR-0024), not a separate batch parser — so SQL gets the same completion / highlighting / hints / parse-errors as the DSL; mode gates the SQL forms; DDL routes through the typed `Command` executor (metadata + type vocabulary preserved), DML and `SELECT` execute as validated SQL; engine-neutral posture, the DSL→SQL teaching echo; supersedes ADR-0001's `sqlparser-rs` reservation; phased plan (`Q1` / `Q2` / `Q4`)
 - [ADR-0031 — The SQL expression grammar](0031-sql-expression-grammar.md) — **Accepted**, the stratified SQL expression grammar fragment commissioned by ADR-0030 §3: a single precedence ladder (`OR`/`AND`/`NOT`, the comparison/`LIKE`/`IN`/`BETWEEN`/`IS NULL` predicate set, arithmetic incl. `||`, function calls, `CASE`) — the superset of ADR-0026's DSL `WHERE` grammar, authored as a parallel fragment so simple mode is untouched; pure validation, builds **no** AST (consumers run/store SQL as text per ADR-0030 §4/§6); reuses ADR-0026's `Subgrammar` recursion + depth cap unchanged; subquery expressions and qualified column refs deferred to ADR-0030 Phase 2
+- [ADR-0032 — The full SQL `SELECT` grammar](0032-sql-select-grammar.md) — **Accepted**, the Phase-2 grammar commissioned by ADR-0030 §3: full `SELECT` with `INNER`/`LEFT`/`RIGHT`/`FULL OUTER`/`CROSS` joins, `GROUP BY`/`HAVING`, all four set ops (`UNION`/`UNION ALL`/`INTERSECT`/`EXCEPT`), `WITH` and `WITH RECURSIVE` CTEs, `LIMIT … OFFSET`, `DISTINCT`, `t.*`, and bare-alias projection (lifting Phase-1 §4.2); additive extensions to ADR-0031's `sql_expr` for scalar subqueries, `IN (SELECT …)`, `[NOT] EXISTS`, and qualified column refs (redeeming ADR-0031 §7 OOS-1/OOS-2); grammar-recursion via `Subgrammar(&SQL_SELECT_COMPOUND)` reuses ADR-0026's `MAX_SUBGRAMMAR_DEPTH = 64` cap unchanged; **softens ADR-0030 §8's "ambient assistance comes for free" claim**: completion scope needs new `WalkContext` accumulators (a `from_scope_stack` of `ScopeFrame`s holding `from_scope` / `cte_bindings` / `projection_aliases`), a **new walker node variant `Node::ScopedSubgrammar(&Node)`** as the push/pop trigger (existing `Node::Subgrammar` unchanged so DSL `Expr` and `sql_expr` recursion are unaffected), qualified-prefix completion narrowing, body-projection-derived CTE column resolution (so `SELECT *` and explicit-projection CTE bodies both yield real column completion past `cte_alias.|`), and a **post-walk fixup pass** that re-resolves projection-list identifier highlighting/validity once `FROM` is parsed (the projection-before-FROM problem); classifies every Phase-2 validation case against ADR-0027's ERROR/WARNING guideline (§11): five new `diagnostic.*` keys for parse-time-detectable cases (unknown qualifier, ambiguous column, projection-alias misplaced, CTE/compound arity mismatch) plus eight `engine.*` translation keys; a MatchedPath-walking predicate-warnings variant that closes the Phase-1 gap where SQL `WHERE` expressions emitted no `LIKE`-on-numeric / `= NULL` / type-mismatch warnings (ADR-0027 Amendment 1 finally extends to the SQL surface); adds a worker-side post-prepare type-resolution pass via engine column-origin metadata so bare column refs recover their playground type (partially lifting Phase-1 §4.5, the bool→0/1 case) — `Cargo.toml` gains `column_metadata` to rusqlite features (verified against pinned 0.39.0); `__rdbms_*` rejection extended to every new table-source slot