Implement #!fold-case / case-insensitive parsing (R7RS §2.1)

[aalpar]

Context

TODO at machine/compile_time_continuation.go:424:

// TODO: implement case-insensitive parsing by creating parser with caseInsensitive=true

Problem

R7RS §2.1 specifies #!fold-case and #!no-fold-case directives that control case sensitivity of subsequent identifiers. The parser already has a caseInsensitive parameter, but the compile-time continuation code that invokes the parser doesn't use it. This means #!fold-case has no effect at compile time.

Suggested approach

1. Thread the case-sensitivity flag through the compile-time continuation's parser creation
2. Ensure #!fold-case / #!no-fold-case directives toggle the flag during tokenization
3. Add tests for case-folded identifiers in include and include-ci forms

R7RS reference

The directive #!fold-case causes subsequent identifiers and character names to be case-folded. The directive #!no-fold-case reverses the effect.