feat(mhfu-port): the MHP3rd porter, built from a manifest on mhp-formats

[sp00ktober]

Part of sp00ktober/MHFU-ModKit#63. GPL-3.0-or-later.

• mhfu-port build|inject ports/<name>.toml: the manifest is the only input. inject hands the bytes to mhfu.inject under the manifest's pac name.
• build is port_monster as steps: donor, host, record map, rig (rig, retarget), skin and PMO (skin, mesh), motion, PAC. constraints checks the engine's rules before it writes.
• fk: the one engine FK, matched to the old copies within 1e-12; the studio (sp00ktober/MHFU-ModKit#67) and Blender (sp00ktober/MHFU-ModKit#70) move onto it.
• manifest: the whole schema, read with tomllib, written with tomli-w. ports/*.toml carry no comments. Derived keys (host_frame, fid, orig, em_id, animated) and dead ones (hops, reweight_undriven) are gone, and so is the Tigrex hitzone table the Zinogre's manifest copied from the game.
• mhfu-port diff OLD NEW: two builds compared group by group and clip by clip.
• mhfu: inject takes the file name a Lua mod expects and names the .orig; Extracted.find reads another game's variable.

Against today's builds, mhfu-port diff finds only fixes:

Fix	Brute (88 groups)	Zinogre (181)
Source strips drawn twice, the next dropped	8 groups	19
Mirrored triangles in lists	45 (+2 in strip groups)	57 (+8)
Loop starts carried	8 clips × 3 parts	5 × 3 (2 of 7 sit in slots the host leaves empty)
Vertex scale 32768/128; header scale was (clip, sx, sy)	< 0.5 step; one group no longer clamped (0.026)	< 0.5 step
The donor mesh's UV scale and offset applied	–	group 133, 20 vertices
Layout: strips instead of a PRIM per triangle, 16-aligned buffers, the host PAC's 432-byte tail kept	PMO 76048 → 68480 B	120000 → 107648 B

Skeleton, textures, skin weights and the other entries are identical. Also fixed: skip_bones reaches the build; retarget mode maps records by the record table instead of by position; a second root at bone 1 hung the partition (275 of 2122 MHP3rd skeletons).

Test plan

• uv run pytest with and without MHFU_DATA/MHP3RD_DATA; both manifests build to pinned hashes
• Variants (auto, transfer, retarget, both donors) against the old builder: only the fixes above, and the Zinogre retarget's record map
• In game after a cold boot, both ports render and animate. Open, as in today's builds: the Zinogre stands slightly below the ground, and the Brute's severed tail floats beside him.

🤖 Generated with Claude Code