v1.0.0: feat: implement full ssh_config(5) spec compliant Go library

- Complete OpenSSH client configuration parsing following ssh_config(5)
- Tristate type for proper boolean handling (Unset/No/Yes)
- Full Match directive with all criteria (host, user, exec, canonical, final, tagged, localnetwork, etc.)
- Complete token expansion (%%, %d, %h, %i, %L, %l, %n, %p, %r, %u, %C)
- Conditional Include inside Host/Match blocks with inherited conditions
- IgnoreUnknown directive support
- CanonicalizeHostname with DNS resolution and re-parsing
- Tag directive and Match tagged support
- ProxyCommand with proper net.Conn implementation
- Well-organized codebase (types, parser, matcher, expand, canonicalize)
- Comprehensive test coverage
- MIT License