Import art/VFX asset packs + game-feel systems; normalize texture extensions to lowercase for LFS

Add BefourStudios SciFi environment packs, Gabriel Aguiar VFX, and the
ShaderCrew Toon Shader embedded packages, plus combat/enemy/wave/death
gameplay systems and supporting vault docs/screenshots.

Rename 11 vendor textures from uppercase .PNG/.HDR to lowercase so the
case-sensitive Git LFS filters (*.png/*.hdr) match on case-sensitive
filesystems (Linux CI, case-sensitive macOS), not just locally where
core.ignorecase=true masks the gap. Each .meta moved with its asset so
GUID references are preserved. All ~1000 binaries tracked via LFS.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Packages/com.shadercrew.the-toon-shader.core/README for Samples.md.meta

@@ -0,0 +1,14 @@
+fileFormatVersion: 2
+guid: c4ab73ec551266f428994d9974034cc3
+TextScriptImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 
+AssetOrigin:
+  serializedVersion: 1
+  productId: 269238
+  packageName: The Toon Shader
+  packageVersion: 1.4.2
+  assetPath: Packages/com.shadercrew.the-toon-shader.core/README for Samples.md
+  uploadId: 919972