Initial commit: Odin editor client + Kotlin daemon prototype

Native SDL3 editor written in Odin with a piece-table buffer core,
backed by a Kotlin/JVM daemon speaking newline-delimited JSON over
localhost TCP for Gradle import, Kotlin/Java diagnostics, and
heuristic completion/hover/definition/references/rename.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/shader-toolchain.md

@@ -0,0 +1,40 @@
+# SDL3 GPU Shader Toolchain
+
+SDL3 GPU accepts different shader formats depending on the selected backend:
+
+- Vulkan: SPIR-V
+- D3D12: DXBC or DXIL
+- Metal: MSL or metallib
+
+For this Linux-first prototype, use GLSL compiled to SPIR-V with `glslc` from shaderc.
+
+```sh
+scripts/compile-shaders.sh
+```
+
+Outputs are written to `client/odin/shaders/compiled/` and intentionally ignored by git.
+
+Fedora install:
+
+```sh
+sudo dnf install glslc
+```
+
+Cross-platform path later:
+
+- Use SDL_shadercross for offline conversion from SPIR-V or HLSL to backend-specific shader formats.
+- Keep source shaders in git.
+- Generate SPIR-V/DXIL/MSL in CI or release packaging.
+- At runtime, choose the shader blob matching `SDL.GetGPUDeviceDriver(device)` or `SDL.GetGPUShaderFormats(device)`.
+
+Current recommendation:
+
+- Build Linux/Vulkan first with checked-in GLSL sources and generated SPIR-V as build artifacts.
+- Add SDL_shadercross only when Windows/macOS backends matter.
+
+Current renderer state:
+
+- The editor loads `rect.vert.spv` and `rect.frag.spv` for the direct SDL3 GPU path.
+- The editor loads `text.vert.spv` and `text.frag.spv` for font-atlas text.
+- Text is rendered from a baked `stb_truetype` atlas using `/usr/share/fonts/google-noto/NotoSansMono-Regular.ttf`.
+- A later portability step should bundle a project font or add configurable font discovery.