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>

client/odin/shaders/rect.frag.glsl

@@ -0,0 +1,8 @@
+#version 450
+
+layout(location = 0) in vec4 v_color;
+layout(location = 0) out vec4 out_color;
+
+void main() {
+    out_color = v_color;
+}