Fix IMPACT UI rendering, pixel transfers, and PS/2 key repeat

[iblowmymind]

IRIX graphics applications exposed several missing IMPACT pixel-transfer, bitmap, and indexed-color behaviors: black or red interfaces, transparent menu highlights, malformed icons and brush images, cursor trails, and corrupted canvas or menu restores. This PR implements those paths and honors the PS/2 keyboard mode commands that let X manage repeat for held application controls.

The changes are split into eight commits, one fix per commit:

• Preserve RGBA component order in GE framebuffer readback.
• Handle general bitmap row batches and bitmap moves used by StudioTools 13.
• Honor PS/2 set-3 global and per-key repeat/break modes, preserve them in snapshots, and suppress repeated host make events when the guest disables hardware repeat.
• Treat native X CI12 pixels as color indices in both the RSS interpreter and JIT.
• Preserve full X overlay indices so Maya popup highlights remain opaque.
• Apply FIFO image-pixel formatting and discard transport padding between rows.
• Restore image dimensions when packed transport rows differ from the destination rectangle, fixing Amazon icons and StudioPaint brush/cursor transfers.
• Distinguish RGBA and ABGR framebuffer readback modes, fixing channel-swapped restores in Dynamation and StudioPaint.

Validation:

• Release IMPACT tests: 134 passed, with 2 benchmark tests ignored. PS/2 tests: 8 passed.
• Clean release CLI build and git diff --check passed.
• Live testing in IRIX on a disposable disk clone with RSS JIT enabled: Marquee license dialog and main UI; StudioTools 13 text and icons; Maya 6.5 menu, Save As dialog, and workspace-picker highlights; Amazon icons and brush strokes; StudioPaint cursor movement, brush strokes, and Space-held panning; Dynamation icons and menu redraw/restoration; and Vizpaint2D painting.
• Wavefront Model's graphical editor renders a newly created cube in wireframe and flat shading with a gray viewport and visible viewport controls. Preview's editor and playback were also checked; the reported cyan viewport was not reproduced in the tested build.
• Guest X event checks confirm normal text repeat still works, while repeated host makes produce a single press/release when X disables repeat. StudioPaint's held Space control was also exercised through the emulator's PS/2 input path.

[Samueltgg12]

@techomancer looks good, can be cleanly merged without a problem.