[givethesourceplox]

What and why

Extend the optional compressed-texture quality path from #1319 to omit one, two or three finest mip levels. DM_NVN_TEX_MIP_SKIP=<pixels> sets the width-and-height threshold; new DM_NVN_TEX_MIP_LEVELS=1..3 selects the reduction while always retaining at least one level. The feature remains off by default.

Keep the original coarser mip contents during upload, translate guest mip levels for views/copies/readbacks/sparse clamps, and refuse copies of removed levels. Recognize reduced textures only when both dimensions and mip count match an eligible compressed chain, avoiding accidental remapping of unrelated size differences. Compressed IMAGE resources retain read-only usage; shader-written textures and uncompressed render formats remain unchanged. Zero-block accounting indexes the retained host levels.

This deliberately trades close-up texture detail and original texture-size queries for reduced texture storage. It changes texture quality, not internal render resolution, and does not claim to fix the complete GPU or thermal bottleneck.

Dependency: the texture upload/view/copy portion of #1319, originating in fc815c3, is included as the separate prerequisite commit 4b13851. Credit for that one-level path belongs to #1319 (JioChoi). The next commit contains this multi-level extension, stricter recognition and fixture. Pool thresholds, raw-residency policy and other #1319 changes are excluded. The read-only compressed-image correction and SDK-26 MetalFX declaration prerequisite overlap #1404.

Reference finding.

Checked

Apple M1 Pro, macOS 26.5.2, Xcode 26.5:

• check_t_texture_quality: 18 checks in each of four processes, all pass with Metal API validation: reduction off, and levels 1, 2 and 3 at threshold 512. A five-level BC1 texture has different data in each mip; GPU readback verifies retained contents and dimensions. Also checks guest-to-host mip mapping, removed-level copy refusal, minimum one retained mip, and unchanged small/uncompressed/shader-written/volume textures.
• Documentation tests: 11 pass; chain tests: 17 pass; environment-switch registry: one test passes; git diff --check passes.
• LLVM static analysis: no new findings.
• No translation-chain or shader-profile inputs changed; no game shader rebuild.

No standalone Ocarina gameplay, isolated memory/FPS/thermal measurement or iPhone result is claimed for this branch. The local harness has only DK, MKW and Ocarina, no stored baselines and no DK/Ocarina smoke routes on this base. Cross-game runtime behavior, sparse streaming and explicit view/copy workloads still need broader coverage; the fixture verifies uploads and level-selection semantics.

Docs

• Rendering reference and player environment-switch registry updated; symptom index regenerated.
• Shader chain unchanged.
• No game files, keys or extracted data included.