Introduce a fail(p, "msg") inline function that stores the error message
in a buffer and longjmps, replacing ~52 fprintf(stderr,...)+longjmp pairs.
The error message is propagated through Ast.err_msg so callers can decide
whether/how to display it. Also add forward declarations for all static
functions and move PtrModifiers typedef to the type definitions section.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Replace 32 parse-error exit(1) calls with longjmp to allow callers to
detect and handle parse failures. The OOM exit(1) in
astNodeListEnsureCapacity is kept as-is.
Add has_error flag to Ast, wrap parseRoot() with setjmp in astParse(),
and update test infrastructure to use the C parser for testError tests.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
