feat(core): store code snippets during indexing

[prosdev]

Summary

Implements #67 - First sub-issue of Epic #66 (Richer Search Results)

Changes

packages/core/src/scanner/types.ts

• Added snippet?: string field to DocumentMetadata interface

packages/core/src/scanner/typescript.ts

• Added DEFAULT_MAX_SNIPPET_LINES constant (50 lines)
• Added truncateSnippet() helper method
• Updated all extraction methods to capture full code content:
  • extractFunction
  • extractClass
  • extractMethod
  • extractInterface
  • extractTypeAlias

packages/core/src/scanner/__tests__/scanner.test.ts

• Added 7 new tests for snippet extraction:
  • Extract snippets for classes
  • Extract snippets for functions
  • Extract snippets for interfaces
  • Extract snippets for type aliases
  • Extract snippets for methods
  • Truncate long snippets
  • Preserve formatting and indentation

Behavior

The scanner now captures actual code content, not just metadata:

• Small components (<50 lines): Full code content stored
• Large components (>50 lines): Truncated with // ... N more lines indicator
• Formatting: Original indentation and formatting preserved

Testing

• All 28 scanner tests pass
• TypeScript compiles without errors
• Biome linting passes

Related Issues

• Closes Store code snippets during indexing #67
• Part of Epic Epic: Richer Search Results #66