v1.2.0

Breaking: ISO-2.0's trailer now requires the tagged Name = Value format (same as the header), not XML, per the final draft of ISO 25178-71:2026. SdfDialect.requires_xml_trailer and SdfFile.trailer_xml are removed.

Breaking: CLI -r/--remove-trailer is removed. -x/--fix-trailer now handles all trailer clean-up, dialect-aware (tagged-format salvage for ISO-2.0, ASCII-only fixups otherwise).

Added SdfFile.trailer_fields to read/write the trailer as a dict of tagged fields, and exported parse_tagged_fields, format_tagged_fields, sanitize_tagged_fields, validate_trailer_ascii, validate_trailer_tagged at the top level.

Fixed: reading a file no longer fails because of a malformed or non-ASCII trailer; only writing still validates it.

Fixed: a spurious blank line before the trailer's closing * in ASCII output.