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

tree-sitter-storybook/grammar.js

@@ -50,7 +50,7 @@ module.exports = grammar({
       $.enum_declaration,
       $.concept_declaration,
       $.sub_concept,
-      $.concept_comparison
+      $.definition
     ),
 
     // Use declarations
@@ -548,9 +548,9 @@ module.exports = grammar({
 
     any_type: $ => 'any',
 
-    // Concept comparison - compile-time pattern matching
-    concept_comparison: $ => seq(
-      'concept_comparison',
+    // Definition - compile-time pattern matching
+    definition: $ => seq(
+      'definition',
       field('name', $.identifier),
       '{',
       commaSep1($.variant_pattern),