Drop dead Git LFS assets with never-uploaded objects

Remove 158 LFS-tracked files whose objects never reached origin
(incomplete push) and so couldn't be fetched on a fresh checkout:
Rukhanka Samples~/ demo assets (Unity-ignored), editor inspector
icons + RukhankaAnimation.pdf, and 2 doc screenshots. All editor-only
or Unity-ignored; verified non-essential (clean compile, 390/390 tests,
clean netcode boot without them). Each asset removed with its .meta.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Packages/com.rukhanka.animation/Samples~/Samples/SampleAssets/Spitter/Models/Spitter.fbx

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Packages/com.rukhanka.animation/Samples~/Samples/SampleAssets/Spitter/Textures/Spitter_Albedo.tif

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Packages/com.rukhanka.animation/Samples~/Samples/SampleAssets/Spitter/Textures/Spitter_MetallicSmooth.tif

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Packages/com.rukhanka.animation/Samples~/Samples/SampleAssets/Spitter/Textures/Spitter_Normal.tif

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