walker: populate cte_bindings placeholders + projection_aliases (ADR-0032 §10.3 stage 1 / §10.4)

Sub-phase 2b checkpoints 4 and 5 combined — adds the
placeholder CTE binding push (§10.3 stage 1) and the
projection alias accumulator (§10.4).

Node::Ident gains two more flags, mechanically applied to
every existing site:

- `writes_cte_name: bool` — push a placeholder `CteBinding`
  (name only, empty columns) onto the top `ScopeFrame`'s
  `cte_bindings`. Set on `CTE_NAME_IDENT` in sql_select.rs.
  Fires BEFORE the body's `ScopedSubgrammar` enters (the
  CTE-def Seq's ident slot precedes the body's `(`), so the
  body can self-reference the CTE name as a valid table source
  (WITH RECURSIVE).
- `writes_projection_alias: bool` — append the matched name to
  the top frame's `projection_aliases`. Set on
  `PROJECTION_BARE_ALIAS_IDENT` so both the AS-form
  (`a AS alpha`) and bare-form (`a alpha`) paths capture
  cleanly. The ident is shared by both paths through
  `PROJECTION_AS_ALIAS` and the lookahead factory, so
  capturing on the ident itself covers both forms with no
  duplication.

The §10.3 stage-2 harvest (deriving CTE output columns from the
body's projection per the six derivation rules in the ADR's
table) is structurally deferred — the placeholder's `columns`
stays empty until the harvest is wired. This is intentional
scope honesty: the placeholder-name presence is sufficient for
the schema-existence diagnostic (2d) to recognize CTE names as
valid table sources, and the qualified-prefix completion (2e)
will populate the columns when the harvest hook is added there.
Tests below assert the placeholder-name behavior; the
column-derivation tests from plan §2b's exit gate will be
satisfied incrementally as later sub-phases need them.

Tests (8 new, all green):

- Single CTE → one placeholder binding with the matched name.
- Multiple CTEs → placeholders in declaration order.
- Recursive CTE → name visible inside body (the body's
  `from r` reference parses; verified by the walk completing).
- Projection aliases via AS form → captured into the top
  frame's `projection_aliases`.
- Projection aliases via bare form → captured.
- Mixed alias forms → captured in projection order, with
  unaliased projection items absent from the alias list.
- No aliases → empty `projection_aliases`.
- CTE body aliases do not leak to outer scope (the body's
  frame pops on `ScopedSubgrammar` exit, taking its
  projection_aliases with it).

All 1358 previous tests still pass. Test totals: 1366
passing, 0 failed, 1 ignored. Clippy clean.

This closes out the scope-accumulator side of sub-phase 2b.
The remaining 2b-style work — full CTE column-derivation
harvest per §10.3's six rules — folds into 2d (where the
arity-check pass needs declared-vs-derived column counts) and
2e (where qualified-prefix completion needs CTE columns).

src/dsl/grammar/data.rs

@@ -39,6 +39,8 @@ const TABLE_NAME_EXISTING: Node = Node::Ident {
     writes_column: false,
         writes_user_listed_column: false,
 writes_table_alias: false,
+writes_cte_name: false,
+writes_projection_alias: false,
 };
 
 /// Table-name slot variant that populates
@@ -54,6 +56,8 @@ const TABLE_NAME_INSERT: Node = Node::Ident {
     writes_column: false,
         writes_user_listed_column: false,
 writes_table_alias: false,
+writes_cte_name: false,
+writes_projection_alias: false,
 };
 
 // =================================================================
@@ -113,6 +117,8 @@ static FORM_A_COLUMN: Node = Node::Ident {
     writes_column: false,
     writes_user_listed_column: true,
 writes_table_alias: false,
+writes_cte_name: false,
+writes_projection_alias: false,
 };
 static INSERT_COMMA: Node = Node::Punct(',');
 
@@ -225,6 +231,8 @@ const TABLE_NAME_WRITES: Node = Node::Ident {
     writes_column: false,
         writes_user_listed_column: false,
 writes_table_alias: false,
+writes_cte_name: false,
+writes_projection_alias: false,
 };
 
 /// Column-name slot in `set col = …` — resolves the column's
@@ -239,6 +247,8 @@ const SET_COLUMN: Node = Node::Ident {
     writes_column: true,
     writes_user_listed_column: false,
 writes_table_alias: false,
+writes_cte_name: false,
+writes_projection_alias: false,
 };
 
 /// Value slot resolved at walk time from
@@ -395,6 +405,8 @@ const SELECT_ALIAS_IDENT: Node = Node::Ident {
     writes_column: false,
     writes_user_listed_column: false,
 writes_table_alias: false,
+writes_cte_name: false,
+writes_projection_alias: false,
 };
 static SELECT_AS_ALIAS_NODES: &[Node] = &[
     Node::Word(Word::keyword("as")),
@@ -439,6 +451,8 @@ const SELECT_FROM_TABLE: Node = Node::Ident {
     writes_column: false,
     writes_user_listed_column: false,
 writes_table_alias: false,
+writes_cte_name: false,
+writes_projection_alias: false,
 };
 
 /// `where <sql_expr>`.