Release v0.2.0

Added

• xor and and options for mutually exclusive and dependent flags.
• counter option for integer occurrence counting, including repeated short flags and explicit numeric increments.
• io-* tags (io, io-kind, io-stream, io-open) for string option/positional input/output templates with validation; positional auto/stream modes support stdin/stdout fallback.
• CommandChain parser option for executing active commands from parent to leaf while keeping leaf-only command execution as the default.
• validate-* tags for string, path, and numeric post-parse validation on options and positional arguments.
• Numeric required ranges for repeatable options, allowing slice and map flags to require value counts.
• Documentation site structure with focused topic pages and broader public API coverage.

Changed

• ParseArgs now re-runs duplicate flag/command validation only when parser metadata is dirty (after mutations/rebuild/config changes), reducing overhead for reused parser instances.
• User-facing error messages now use symmetric backtick quoting instead of legacy `value' quoting.