- Simplified chunk region notation from @head/@body/@tail/@decl to ^/~ suffix format across all modules.
- Removed ChunkRegion::Tail and ChunkRegion::Decl enum variants and updated region matching logic accordingly.
- Added call-with-callback pattern detection via try_promote_call_with_callback() and trailing_callback_body() functions.
- Updated documentation and test fixtures to reflect new region selector syntax throughout codebase.