Fix Director text decoding and leading whitespace layout

[luismgl]

Summary

• Decode XMED text using the platform declared by each Director file: Mac Roman for platform 1 and Windows-1252 otherwise.
• Preserve valid UTF-8 before applying the legacy single-byte fallback.
• Propagate the encoding through internal and external cast loading and the JS chunk-inspection path.
• Preserve authored leading whitespace in styled PFR text layout so its advance contributes to glyph positioning.

Rationale

Classic Mac Director movies can store accented text as Mac Roman bytes. Treating those bytes as Windows-1252 produces incorrect glyphs. Separately, some Director text members use leading whitespace as authored positioning inside the member rectangle; dropping it collapses otherwise distinct glyph runs onto the same origin.

Both changes are format/runtime rules and do not alter the public polyfill API or rely on movie names, member IDs, or character heuristics.

Validation

• Rust tests cover Mac Roman and Windows-1252 critical bytes, ASCII, valid UTF-8, platform selection, and leading-whitespace advances.
• npm run build-vm
• npm run build-polyfill
• Browser validation with DPR 2 and a 1024x550 logical canvas confirmed corrected accented text, preserved initial text spacing, unchanged final-grid layout, keyboard progression, and hover behavior.

[chameleonxxl]

For which movie did you make those changes?

Would be good to know in order to test it properly