walker: SQL diagnostics — multi-binding scope, qualified refs, Phase-1 gap closure (sub-phase 2d)

Implements the bulk of ADR-0032 §11 diagnostics. The
schema-existence pass becomes multi-binding-aware; the SQL
predicate-warning pass closes the Phase-1 carry-over gap
named in §11.6; pre-flight duplicate-CTE detection lands
(user-approved Plan §Open-2); a `data::WITH` CommandNode
makes WITH-prefixed statements dispatch through the registry.

Catalog (`src/friendly/strings/en-US.yaml`, `src/friendly/keys.rs`):

- Six new `diagnostic.*` keys: ambiguous_column,
  compound_arity_mismatch, cte_arity_mismatch, duplicate_cte,
  projection_alias_misplaced, unknown_qualifier.
- Eight new `engine.*` translation keys (ADR-0032 §11.5) for
  the friendly-error layer to render engine messages in
  engine-neutral wording. The catalog entries are authored;
  wiring them into the engine-error path is deferred (the
  friendly layer reads these by key when reached).

Schema-existence diagnostic (`schema_existence_diagnostics`)
extended per ADR-0032 §11.2:

- A pre-pass collects all `table_name` / `cte_name` / table-
  alias idents into a `PassBinding` vec + a CTE name list,
  sidestepping the projection-before-FROM ordering problem
  (§10.6). The main pass then resolves identifiers against the
  complete scope.
- Bare column references resolve against any binding's
  columns. Zero matches → `diagnostic.unknown_column` (the
  table arg lists all in-scope tables in the multi-binding
  case). Two-or-more matches → `diagnostic.ambiguous_column`.
- Qualified `t.c` refs detect their qualifier via a look-ahead
  on the matched path (Punct '.' + Ident{role:
  sql_expr_qualified_ref} after the leading Ident). Unknown
  qualifier → `diagnostic.unknown_qualifier`; the column check
  then runs against the resolved binding's table.
- The `t.*` qualified-wildcard's `qualified_star_qualifier`
  ident also resolves through the same pass.
- CTE-name references in table-source slots accept silently
  (the CTE binding's columns are unknown until the deferred
  §10.3 stage-2 harvest lands, so bare column refs into a
  CTE binding short-circuit to "accept silently").
- Duplicate CTE names in the same `WITH` block emit
  `diagnostic.duplicate_cte` on the second occurrence
  (Plan §Open-2).

Phase-1 gap closure (`sql_predicate_warnings`, ADR-0032 §11.6):

A new MatchedPath-walking pass that identifies predicate-tail
shapes by node-name labels and emits the same `diagnostic.*`
keys the DSL `Expr` AST pass already emitted (`eq_null`,
`like_numeric`, `type_mismatch`). Scoped to bare column refs
in `<column> <op> <literal>` form — qualified-ref and
expression-operand cases stay un-flagged in this minimal pass,
which is a safe false-negative posture (the warning is
advisory; the engine still runs). Runs alongside the schema-
existence pass on every successful SQL parse — WHERE,
HAVING, JOIN ON, projection, ORDER BY all get warnings
uniformly. Tests cover all three keys plus the negative
"compatible types don't warn" case.

WITH dispatch (`data::WITH`):

`with x as (…) select * from x` now dispatches via the registry
with entry word `with`. Shape: `SQL_WITH_TAIL`, the post-`WITH`
portion of a statement (optional `RECURSIVE`, the cte_def
list, the trailing compound_select, optional `;`). Both
`data::SELECT` and `data::WITH` route to `build_select` and
produce `Command::Select { sql: source }` — execution is
grammar-as-text, so the entry-word split doesn't fork the
exec path. `is_advanced_only` extended to include `with`.

Deferred per the 2d-scoped DA review (documented as a
`(TBD)` in the cross-cut matrix for 2g):

- `diagnostic.projection_alias_misplaced` — requires clause
  detection (the matched-path is flat).
- `diagnostic.compound_arity_mismatch` — needs per-leg
  projection counting.
- `diagnostic.cte_arity_mismatch` — depends on §10.3 stage-2
  harvest, which 2b deferred.
- `engine.*` key wiring into the friendly-error layer — the
  catalog entries are authored; the engine-error path reads
  them by key when reached, but no proactive enhancement of
  the layer here.

Test totals: 1366 → 1382 passing (+16: 10 schema-existence
multi-binding + diagnostic tests, 7 Phase-1 gap closure
tests, minus duplicates from prior runs), 0 failed, 1 ignored.
Clippy clean.

src/friendly/keys.rs

@@ -38,11 +38,27 @@
 /// `(key, expected_placeholders)`. Sorted by key for grep-ability.
 pub const KEYS_AND_PLACEHOLDERS: &[(&str, &[&str])] = &[
     // ---- Pre-submit diagnostics (ADR-0027) ----
+    ("diagnostic.ambiguous_column", &["column", "qualifiers"]),
+    ("diagnostic.compound_arity_mismatch", &["op", "left_n", "right_n"]),
+    ("diagnostic.cte_arity_mismatch", &["cte", "declared", "actual"]),
+    ("diagnostic.duplicate_cte", &["name"]),
     ("diagnostic.eq_null", &[]),
     ("diagnostic.like_numeric", &["column", "type"]),
+    ("diagnostic.projection_alias_misplaced", &["alias", "clause"]),
     ("diagnostic.type_mismatch", &["column", "type"]),
     ("diagnostic.unknown_column", &["name", "table"]),
+    ("diagnostic.unknown_qualifier", &["qualifier"]),
     ("diagnostic.unknown_table", &["name"]),
+    // ---- Friendly-error translations of engine messages
+    // ---- (ADR-0019; ADR-0032 §11.5).
+    ("engine.aggregate_misuse", &["name"]),
+    ("engine.ambiguous_column", &["column"]),
+    ("engine.compound_arity_mismatch", &["op"]),
+    ("engine.group_by_required", &[]),
+    ("engine.no_such_column", &["name"]),
+    ("engine.no_such_table", &["name"]),
+    ("engine.recursive_cte_malformed", &[]),
+    ("engine.scalar_subquery_too_many_rows", &[]),
     // ---- Already-exists collisions (anchor: "already exists") ----
     ("error.already_exists.column.headline", &["table", "column"]),
     ("error.already_exists.relationship.headline", &["name"]),