feat: Complete FastAPI multiline support and resolve DotNet parsing artifacts

[zerochae]

Summary

• ✨ Implement comprehensive FastAPI multiline decorator highlighting with proper end-line detection
• 🐛 Fix critical DotNet parser ripgrep multiline artifacts that were producing malformed endpoint results
• 🏗️ Add realistic FastAPI test fixtures with proper layered architecture structure
• 📝 Document comment filtering enhancement for future implementation

Changes Made

FastAPI Multiline Support

• Enhanced FastApiParser:_extract_path_multiline to return both path and end_line_number
• Fixed multiline decorator highlighting to include closing parentheses/brackets
• Added comprehensive test fixtures in tests/fixtures/fastapi/src/app/presentation/http/controllers/multiline/
• Implemented proper end_line_number calculation for complete decorator block highlighting

DotNet Parser Artifact Resolution

• Critical Fix: Resolved ripgrep multiline artifacts producing results like GET /api/v1/products/)] public class ProductsController...
• Enhanced _extract_route_info to properly handle [HttpGet] + [Route("")] combinations
• Fixed empty Route attribute parsing (e.g., [Route("")] now correctly returns empty string)
• Improved content cleaning to preserve HTTP method + Route attribute pairs while filtering unwanted artifacts
• Narrowed Route attribute search scope to method-level only (avoiding class-level Route conflicts)

Infrastructure Improvements

• Updated meta/types.lua with proper type annotations for new multiline functionality
• Enhanced multiline content cleaning with better artifact detection patterns
• Added TODO.md documenting systematic comment filtering enhancement for all frameworks

Test Results

-- FastAPI: All multiline patterns now highlight complete decorator blocks
@router.get(
    "/users/{user_id}",
    response_model=UserResponse
) ✅ Full highlighting


-- DotNet: Artifacts resolved, proper path extraction
[HttpGet]
[Route("")] → GET /api/v1/products ✅ Clean result

Files Changed

• lua/endpoint/parser/fastapi_parser.lua - Multiline highlighting support
• lua/endpoint/parser/dotnet_parser.lua - Artifact resolution and Route handling
• meta/types.lua - Type annotations update
• tests/fixtures/fastapi/src/app/presentation/http/controllers/multiline/ - Realistic test fixtures
• TODO.md - Comment filtering documentation

Breaking Changes

None. All changes are backwards compatible improvements.

Future Work

• Comment filtering implementation across all frameworks (documented in TODO.md)
• Apply similar multiline highlighting fixes to other frameworks (NestJS, Ktor, etc.)