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/RukhankaAnimation.pdf.meta

@@ -1,14 +0,0 @@
-fileFormatVersion: 2
-guid: 5fc783efb879658498ef7e482d82d827
-DefaultImporter:
-  externalObjects: {}
-  userData: 
-  assetBundleName: 
-  assetBundleVariant: 
-AssetOrigin:
-  serializedVersion: 1
-  productId: 298480
-  packageName: Rukhanka Animation System 2
-  packageVersion: 2.9.0
-  assetPath: Packages/com.rukhanka.animation/RukhankaAnimation.pdf
-  uploadId: 897522