refactor: make completion-drop gate schema-aware for consistency

The candidates_at_cursor "input parses complete" gate — which
suppresses re-suggesting a keyword the user just finished typing —
used the schemaless parse while the rest of the completion path is
schema-aware. A schemaless parse can call a type-/arity-wrong tuple
complete.

The divergence is benign today (the drop only removes a re-offered
keyword equal to the partial, and schema divergence is confined to
value type/arity, which never coincides), but parse with the schema
so the gate matches the rest of the surface and stays correct if the
grammar evolves. Strictly safe: can only ever retain a candidate the
schemaless gate would have dropped, never the reverse.

src/completion.rs

@@ -18,7 +18,7 @@ use crate::dsl::grammar::IdentSource;
 use crate::dsl::types::Type;
 use crate::dsl::walker::outcome::Expectation;
 use crate::dsl::{ParseError, parse_command};
-use crate::dsl::parser::parse_command_in_mode;
+use crate::dsl::parser::parse_command_with_schema_in_mode;
 use crate::mode::Mode;
 
 /// Composite literal candidates whose lexed shape is more than
@@ -333,7 +333,18 @@ pub fn candidates_at_cursor_with_in_mode(
     // `pk` at the end of `create table T with pk`. The
     // optional-suffix case (`save ` → `as`) is preserved
     // because there `partial_prefix` is empty.
-    let input_parses_complete = parse_command_in_mode(input, mode).is_ok();
+    //
+    // Parse *with the schema* (not the schemaless `parse_command_in_mode`)
+    // so "complete" means the schema-aware grammar accepts it — the same
+    // consistency fix as issue #2's ambient-hint fallback. A schemaless
+    // parse can report a type-/arity-wrong tuple as complete and wrongly
+    // gate the drop on. Today the two agree at every position this drop
+    // can fire (the drop only removes a re-offered keyword == partial,
+    // and schema divergence is confined to value type/arity, which never
+    // coincides — see issue #18); schema-aware is the principled, latent-
+    // bug-proof choice and can only ever *retain* a candidate the
+    // schemaless gate would have dropped, never the reverse.
+    let input_parses_complete = parse_command_with_schema_in_mode(input, cache, mode).is_ok();
 
     // Schema-aware probe: one walk yields both the expected set
     // and the table-context snapshot (ADR-0024 §Phase D