Port "zig fmt: respect line breaks in struct field value declaration"
test from upstream parser_test.zig.
Implement in parser.c:
- Slice types ([]T, [:s]T) in parseTypeExpr
- Array types ([N]T, [N:s]T) in parseTypeExpr
- Multiline string literals in parsePrimaryTypeExpr
- Add comments explaining why const/volatile/allowzero pointer
modifiers are consumed (not stored in AST; renderer re-derives
them from token positions)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>