ADR-0024 Phase F (full) step 3: delete legacy parser modules

Removes the last consumers of `dsl::lexer`, `dsl::keyword`, and
`dsl::ident_slot`, then deletes the modules.

- `Theme::token_color(&TokenKind)` deleted along with its test;
  `Theme::highlight_class_color(HighlightClass)` is the sole
  highlight-colour mapper (the walker's `per_byte_class` feeds
  it directly).
- `IdentSource` (`dsl::grammar`) absorbs the schema-list /
  expected-label / round-trip semantics that previously lived
  on `IdentSlot`. Adds `completes_from_schema`, `expected_label`,
  and `from_expected_label` methods. The walker's
  `Expectation::Ident { source }` and the schema-lookup request
  on the database worker now share one enum.
- `SchemaCache::for_slot(IdentSlot)` → `for_source(IdentSource)`.
- `Database::list_names_for` and the `Request::ListNamesFor`
  worker variant take `IdentSource`. Internal tables and column
  / relationship lookups dispatch on the same enum.
- `InvalidIdent.slot: IdentSlot` → `InvalidIdent.source: IdentSource`.
  The `invalid_ident_at_cursor` rendering branch in
  `input_render.rs::ambient_hint` updates accordingly.
- Completion's keyword filter (`Keyword::from_word`) becomes
  "backticked items whose payload is all ASCII alphabetic" —
  punct and digit literals still surface through their own
  candidate sources (composite-literal, flag, schema-ident);
  the alphabetic filter excludes them from the keyword bucket.
- `friendly::keys::tests::keyword_and_punct_have_complete_token_vocabulary`
  is dropped. It cross-checked `Keyword::ALL` / `Punct::ALL`
  against catalog entries; both enums are gone. The
  `parse.token.keyword.*` / `parse.token.punct.*` catalog
  entries themselves survive for one more commit (catalog
  cleanup, ADR-0024 §cleanup-pass); the
  `keys_validate_against_catalog` test still pins them.
- Modules deleted: `src/dsl/lexer.rs`, `src/dsl/keyword.rs`,
  `src/dsl/ident_slot.rs`.

Tests: 806 passing, 0 failing, 1 ignored. The drop from 852
reflects the removed module-internal tests (~32 lexer, 7
keyword, 4 ident_slot, 1 theme token_color, 1 friendly keys
keyword/punct), and is the expected outcome.

Clippy clean with `nursery` lints + `-D warnings`.

src/theme.rs

@@ -19,7 +19,6 @@
 use ratatui::style::Color;
 
 use crate::dsl::grammar::HighlightClass;
-use crate::dsl::lexer::TokenKind;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Background {
@@ -106,23 +105,6 @@ impl Theme {
         }
     }
 
-    /// Map a `TokenKind` to its display colour for ambient
-    /// highlighting (ADR-0022 §3). Lex-error tokens always render
-    /// in `tok_error`, regardless of the parse-time error overlay
-    /// applied separately by the renderer.
-    #[must_use]
-    pub const fn token_color(&self, kind: &TokenKind) -> Color {
-        match kind {
-            TokenKind::Keyword(_) => self.tok_keyword,
-            TokenKind::Identifier(_) => self.tok_identifier,
-            TokenKind::Number(_) => self.tok_number,
-            TokenKind::StringLiteral(_) => self.tok_string,
-            TokenKind::Punct(_) => self.tok_punct,
-            TokenKind::Flag(_) => self.tok_flag,
-            TokenKind::Error(_) => self.tok_error,
-        }
-    }
-
     /// Map a walker `HighlightClass` to its display colour
     /// (ADR-0024 §architecture, Phase F). This is the walker-side
     /// equivalent of `token_color` — the renderer consumes
@@ -152,8 +134,6 @@ impl Default for Theme {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::dsl::keyword::{Keyword, Punct};
-    use crate::dsl::lexer::LexError;
 
     #[test]
     fn dark_theme_token_colours_differ_from_background() {
@@ -190,50 +170,14 @@ mod tests {
     }
 
     #[test]
-    fn token_color_maps_each_kind_to_the_expected_field() {
+    fn highlight_class_color_maps_each_variant() {
         let t = Theme::dark();
-        assert_eq!(
-            t.token_color(&TokenKind::Keyword(Keyword::Create)),
-            t.tok_keyword,
-        );
-        assert_eq!(
-            t.token_color(&TokenKind::Identifier("Customers".to_string())),
-            t.tok_identifier,
-        );
-        assert_eq!(
-            t.token_color(&TokenKind::Number("42".to_string())),
-            t.tok_number,
-        );
-        assert_eq!(
-            t.token_color(&TokenKind::StringLiteral("hi".to_string())),
-            t.tok_string,
-        );
-        assert_eq!(
-            t.token_color(&TokenKind::Punct(Punct::Colon)),
-            t.tok_punct,
-        );
-        assert_eq!(
-            t.token_color(&TokenKind::Flag("all-rows".to_string())),
-            t.tok_flag,
-        );
-        assert_eq!(
-            t.token_color(&TokenKind::Error(LexError::UnknownChar('$'))),
-            t.tok_error,
-        );
-    }
-
-    #[test]
-    fn lex_error_tokens_render_in_tok_error_regardless_of_kind() {
-        let t = Theme::dark();
-        for err in [
-            LexError::UnknownChar('$'),
-            LexError::UnterminatedString,
-            LexError::BadFlag,
-        ] {
-            assert_eq!(
-                t.token_color(&TokenKind::Error(err)),
-                t.tok_error,
-            );
-        }
+        assert_eq!(t.highlight_class_color(HighlightClass::Keyword), t.tok_keyword);
+        assert_eq!(t.highlight_class_color(HighlightClass::Identifier), t.tok_identifier);
+        assert_eq!(t.highlight_class_color(HighlightClass::Number), t.tok_number);
+        assert_eq!(t.highlight_class_color(HighlightClass::String), t.tok_string);
+        assert_eq!(t.highlight_class_color(HighlightClass::Punct), t.tok_punct);
+        assert_eq!(t.highlight_class_color(HighlightClass::Flag), t.tok_flag);
+        assert_eq!(t.highlight_class_color(HighlightClass::Error), t.tok_error);
     }
 }