fix: Tecan Magellan - support compact Magellan Pro 7.5 exports

[tamargrey]

Summary

Magellan Pro v7.5 can produce a compact measurement metadata block that omits the Unit:, Number of flashes, and trailing Meas. temperature fields expected by the Tecan Magellan parser. The parser consequently consumed the remaining metadata and raised Expected non-null value.

This change:

• Supports the compact v7.5 metadata layout without changing the existing parsing path.
• Infers Absorbance mode from the measurement section.
• Maps the measurement label and wavelength normally.
• Recovers measurement temperature from the table’s pre-data temperature row.
• Uses the bracketed plate description as the plate identifier.
• Omits number of averages when it is unavailable.
• Preserves plate description, range, and action as custom information.
• Adds a sanitized regression workbook and expected ASM output.

Testing

• Confirmed the original customer workbook converts all 96 wells successfully.
• Ran hatch run test tests/parsers/tecan_magellan/to_allotrope_test.py.
• Ran hatch run lint.

[tamargrey]

Closing in favor of PR with verified commits #1258