Release adaptive widescreen for Mega Man X v1.5.0

[mstan]

Replace the original 16:9 renderer with the accepted adaptive widescreen implementation and release it as v1.5.0. The widescreen Mod follows the window aspect ratio, with fixed 16:9, 21:9 and 32:9 choices and configurable HUD anchoring. Existing activation settings are preserved; the retired renderer selection is ignored.

The compositor extends stage geometry and sprites while preserving native encounter timing, palettes, effects and cutscene progression. Pause menus remain centered with clean side areas. The owner completed the game through the ending after the reported stage, capsule, boss and cutscene fixes.

Integrate with the current shared desktop host, including save browser and rewind. Preserve both historical MMX v2 save chunks and early RTLS snapshots, and write an unambiguous v3 game chunk. Framework support is merged in RetroPortingToolKit/snesrecomp#90; the game pins the tested support commit on its existing framework base.

Validation:

• Windows and Linux Release builds and renderer/display/policy tests pass.
• Windows save/load, deterministic replay, fresh-process load, legacy saves, save browser and rewind checks pass.
• Saved-scene captures pass at five widths, including the final captive-Zero and post-Mammoth barrier fixes; Linux captures also pass.
• Windows portable ZIP dependency checks and Linux AppImage state-layout checks pass.

Packages contain no ROM or save files. Historical investigation and playtest notes are retained in docs/custom-renderer-spike.md.