fix(fast3d): upload RAW block-load textures by per-line stride, not block size

[bassdr]

Summary

Alt-asset / HD texture-pack textures that are loaded via LoadBlock (button prompts, C-button symbols, etc.) render as garbage stripes or a solid block. Vanilla is unaffected; it only appears with a replacement pack enabled.

Root cause

Regression from #1118. It rewrote ImportTextureRaw's fallback upload to describe the buffer with loaded_texture.line_size_bytes:

uint32_t uploadWidth  = safeLineSizeBytes / 4;
uint32_t uploadHeight = safeLineSizeBytes > 0 ? safeLoadedBytes / safeLineSizeBytes : 0;

For a block-loaded texture, line_size_bytes spans the entire image (a LoadBlock is one contiguous "line"), so this collapses the upload to an N x 1 strip. Instrumented, a 768x256 RGBA32 button replacement (gCBtnSymbolsTex):

fast=false   (block load reports origH = 736/48 = 15 rows -> newH 240 != resH 256)
FALLBACK  upW=188416  upH=1          <- uploaded as 188416 x 1
          altWidth(resultNewLineSize/4)=768   <- correct per-row stride

The fast path is skipped because the block load reports a non-integer original height (736 bytes / 48-byte line = 15.33 -> 15), so resultNewHeight (240) != resource height (256). Before #1118 the fallback used resultNewLineSize / 4 = 768 (correct width).

Fix

Describe the buffer by the per-line HD stride resultNewLineSize (tile line_size x h_byte_scale) -- the true per-row stride for both block and tile loads -- and derive height from the loaded bytes. The OOB clamp added by #1118 is preserved.

uint32_t uploadWidth  = resultNewLineSize / 4;                                          // 768
uint32_t uploadHeight = resultNewLineSize > 0 ? safeLoadedBytes / resultNewLineSize : 0; // 245

Scope and testing

Fixes any alt-asset/HD replacement loaded via LoadBlock. Tested with an Xbox/N64 button texture pack: the in-game equip prompt and C-button symbols now render correctly. Fast-path textures (the vast majority of HD textures) are untouched since they never reach this fallback.

Same root PR (#1118) as #1135.