feat(game): add survivor_game with arena and quarter-view camera

Static arena with 20x20 floor and 4 box obstacles rendered using the
forward PBR pipeline with shadow mapping. Fixed quarter-view camera
at (0, 15, 10) looking at origin.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

examples/survivor_game/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "survivor_game"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+voltex_math.workspace = true
+voltex_platform.workspace = true
+voltex_renderer.workspace = true
+wgpu.workspace = true
+winit.workspace = true
+bytemuck.workspace = true
+pollster.workspace = true
+env_logger.workspace = true
+log.workspace = true