Legacy filter capability: MIPNEAREST

Bounded D3D-LEGACY-TEXTURE-CAPS-AUDIT-20261013 continuation, based on fetched origin/main at 7b15136870328d66a8517b9673efad3fd0941294. This branch changes only fill_primcaps.dwTextureFilterCaps from 0xFF to 0xFB, clearing D3DPTFILTERCAPS_MIPNEAREST (0x04). The backend behavior is unchanged.

Microsoft defines MIPNEAREST as choosing the nearest texel from the appropriate mip level, so sampling the currently bound image alone is insufficient. See the D3DPRIMCAPS contract and the Microsoft SDK constants. The cap bit is distinct from the legacy filter enumeration value D3DFILTER_MIPNEAREST=3.

d3dim_draw_tl_triangle_textured and d3dim_gpu_describe select the stage MAGFILTER, then MINFILTER, then legacy TEXTUREMAG/MIN. They reduce the selected value to a boolean: only value 2 selects linear sampling; value 3 selects point. The software sampler accepts one image's dimensions, pointer and pitch, with no LOD or mip-chain input. Its point branch fetches one texel from that image. The GPU JS lowering sets both min/mag from the same boolean and always sets mip: 0. Thus the common advertised MIPNEAREST capability is unsupported.

Run node test/test-legacy-texture-filter-caps.js. The dedicated standalone source test compiles extracted production WAT with the vendored compiler:

• 90 filter fields across primitive caps, HAL/HEL builders and GetCaps 1/2/3/7, aligned/unaligned buffers, legacy descriptor sizes and memory guards. The DX7 mask becomes 0x030003FB, retaining its point/linear additions.
• 36 backend cases: four filter-state sources, NEAREST/LINEAR/MIPNEAREST, and three stage MIPFILTER values. Verbatim production filter-selection statements and JS sampler lowering execute; the actual software sampler, address helper and bilinear helper execute with an instrumented fixture texel fetch. The checkerboard yields one black point sample or four taps producing 0xFF7F7F7F, always on the bound image.
• Six mutation negatives: restored MIPNEAREST, lost NEAREST, lost LINEAR, unrelated mask clearing, enabled GPU mip selection and reversed software filter selection. The original main source fails specifically on the unsupported MIPNEAREST advertisement.
• In-memory composition with the prior CUBEMAP and BORDER fixes passes.

Evidence and self-contained replay: scratch/runs/20261020-legacy-texture-filter-caps/. The snapshot includes the source, compiler, test, baseline, logs, patch, SDK reference and hashes.

This is extracted-source conformance, not fullVM, public COM dispatch, enumeration callback execution, full device setup, GPU rendering or game qualification. State storage/fog and texel fetch are explicit fixtures; the full draw function and full GPU descriptor are not executed. No runtime403 probe, build, guest, browser or box action was performed.

The one-fix stopping condition leaves other legacy mip bits (0x08/0x10/0x20) and reserved bits unchanged and unqualified. They are not evidence of implemented support. Texture-operation audit is outside this task.

Integration remains coordinator-owned. Preserve pending CUBEMAP f856627b8d6ff022c4713aabb60ea7083ed9f0fc at offset 32 and BORDER 0a63482c363082c95e825b34161f42134831a3a4 at offset 44, along with this new offset-36 change. Neither prior patch is duplicated or integrated here. Their existing exact filter-mask assertions will need reconciliation from 0xFF to 0xFB and DX7 0x030003FF to 0x030003FB; retain the prior note about the cube test's address-mask assertion changing to 0xF7. This new test accepts both pre/post cube and border values.

The fetched base retains laptop WarcraftIII/HeroesII work, including 515897841fde86f9b2e0274387aff10cc9add405 ancestry. Shared HEAD/index and unrelated WIP are outside this branch; no main merge or ledger edit occurs.