Add unit tests for parser and codegen
29 tests covering:
- Parser: binding kinds, variadic patterns, literal tokens, ident
constructs, spread-for detection, escape/template output blocks,
multi-macro files, comment skipping, error reporting (line/col)
- Codegen: proc_macro fn emission, single/structural/variadic patterns,
escape blocks, ident construction, keyword vs non-keyword tokens,
and round-trip tests for the hello and derive_getters examples
https://claude.ai/code/session_01Tppkab4eLsL21asHGjQJoF
Claude
36c85500bd