feat(lang): rename concept_comparison to definition (v0.3.2)

Renames the `concept_comparison` keyword to `definition` across the
entire codebase for better readability and conciseness.

Changes:
- Tree-sitter grammar: `concept_comparison` node → `definition`
- Tree-sitter queries: highlights, outline, and indents updated
- Zed extension highlights.scm updated to match
- Lexer: `Token::ConceptComparison` → `Token::Definition`
- Parser: `ConceptComparisonDecl` rule → `DefinitionDecl`
- AST: `Declaration::ConceptComparison` → `Declaration::Definition`,
  `ConceptComparisonDecl` struct → `DefinitionDecl`
- All Rust source files updated (validate, names, convert, references,
  semantic_tokens, symbols, code_actions, hover, completion)
- `validate_concept_comparison_patterns` → `validate_definition_patterns`
- Example file and test corpus updated
- Spec docs: created SBIR-v0.3.2-SPEC.md, updated TYPE-SYSTEM.md,
  README.md, SBIR-CHANGELOG.md, SBIR-v0.3.1-SPEC.md

zed-storybook/languages/storybook/highlights.scm

@@ -20,7 +20,7 @@
   "state"
   "concept"
   "sub_concept"
-  "concept_comparison"
+  "definition"
 ] @keyword.declaration
 
 ; Keywords - Control flow and modifiers
@@ -83,7 +83,7 @@
 (concept_declaration name: (identifier) @type.concept)
 (sub_concept parent: (identifier) @type.concept)
 (sub_concept name: (identifier) @type.sub_concept)
-(concept_comparison name: (identifier) @type.concept_comparison)
+(definition name: (identifier) @type.definition)
 (variant_pattern name: (identifier) @type.variant)
 (template_declaration species: (identifier) @type.builtin)