feat: initialize cargo workspace with voltex_math, voltex_platform, voltex_renderer

Phase 1 Task 1 - workspace scaffolding with stub crates

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

Cargo.toml

@@ -0,0 +1,19 @@
+[workspace]
+resolver = "2"
+members = [
+    "crates/voltex_math",
+    "crates/voltex_platform",
+    "crates/voltex_renderer",
+    "examples/triangle",
+]
+
+[workspace.dependencies]
+voltex_math = { path = "crates/voltex_math" }
+voltex_platform = { path = "crates/voltex_platform" }
+voltex_renderer = { path = "crates/voltex_renderer" }
+wgpu = "28.0"
+winit = "0.30"
+bytemuck = { version = "1", features = ["derive"] }
+pollster = "0.4"
+env_logger = "0.11"
+log = "0.4"