## Summary
- Replace hand-written character scanning in `document_links.cpp` with
the project's `Lexer` class for finding filename arguments in
preprocessor directives
- Extend `Lexer` to activate `header_name` mode for
`#embed`/`#include_next`, and expose `set_header_name_mode()` for
`__has_include`/`__has_embed` contexts
- Remove unused `Include::filename_range` field (had a latent assert
crash on macro-expanded includes)
- Add `MacroInclude` unit test covering `#include MACRO` scenario
## Test plan
- [x] 498 unit tests pass (including new `MacroInclude` test)
- [x] 119 integration tests pass
- [x] 2/2 smoke tests pass
🤖 Generated with [Claude Code](https://claude.com/claude-code)
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
* **New Features**
* Document links now resolve includes written via macros; directive
parsing recognizes include, include_next, embed and __has_* patterns
more reliably using lexer-driven argument detection.
* **Refactor**
* Removed an internal filename-range field previously stored for include
directives.
* **Tests**
* Added unit tests covering directive argument extraction and
macro-based include linking.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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