feat(mhfu-port): check a port: verify, validate, pose, stretch, floor, fidelity, slots

[sp00ktober]

Part of sp00ktober/MHFU-ModKit#63. Stacked on #8.

• verify PAC --manifest M: the structural audit against the donor (partition, palette joints, fork tear, every vertex's weights); 21/21 on both new builds.
• validate PAC: the engine's rules on any monster PAC; clean on all 49 big monsters.
• pose: donor and port posed joint by joint on fk, no longer Blender-only; worst 0.00 on both builds.
• stretch [--fork], floor --host 75, fidelity, slots, labels.

Old bugs fixed:

• floor ignored rotations and read +2.7 for every monster; full FK reads the host −1.3, the Brute −1.2 and the Zinogre +105. In game the Zinogre stands slightly below the ground at that lift, so floor measures the animation alone and no longer suggests a lift: where the game puts a port is open.
• slots/labels: an empty donor stream parsed as garbage (59 clips on the Brute's stream 2); slots that exist only in stream 2 were missed; moveset pairs were over-attributed (now mhfu.em.moveset).
• verify mapped three Brute bones to the wrong joints (278 false fails); fidelity compared its own replay against itself; stretch counted 695 rigid triangles as growing.

Test plan

• uv run pytest with and without game data
• Old tools against new on both of today's builds and the native Tigrex

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