TOON v3.0 Spec Compliance

[mischasigtermans]

Summary

• Full TOON v3.0 specification compliance
• Official spec test fixtures from toon-format/spec
• Code cleanup: extracted duplicate logic, removed redundant comments
• ~50% token reduction vs JSON (verified benchmarks)

Features Added

• key_folding config: collapse single-key nested objects to dot notation
• key_folding_depth config: limit folding depth
• expand_paths config: expand dotted keys back to nested objects on decode
• Strict mode with detailed validation errors
• Delimiter support (comma, tab, pipe)

Breaking Changes

• String escaping now uses quoted strings ("hello, world") instead of backslash escaping
• Removed escape_style config option

Code Quality

• Extracted shouldSkipKeyValue() to remove 3x duplication in encoder
• Extracted findUnquoted() to remove 5x duplication in decoder
• Added indentStr() caching for performance
• Removed ~40 redundant comments

Test plan

• 470 tests pass
• Benchmarks verified on production data (~53% savings)
• Round-trip fidelity confirmed with production test cases