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>

protocol.md

@@ -0,0 +1,208 @@
+# TCP Protocol
+
+Transport: UTF-8 JSON objects separated by `\n`.
+
+File paths in text and intelligence requests are normalized to absolute daemon-side paths before being used as document keys.
+
+## Request
+
+```json
+{"id":1,"method":"workspace/open","params":{"root":"/home/me/project"}}
+```
+
+## Response
+
+```json
+{"id":1,"ok":true,"result":{"root":"/home/me/project","gradle":true,"modules":[],"sourceRoots":[],"tasks":[]}}
+```
+
+## Error
+
+```json
+{"id":1,"ok":false,"error":{"code":"UNKNOWN_METHOD","message":"No handler for method"}}
+```
+
+## Event
+
+```json
+{"event":"workspace/indexing","params":{"state":"started"}}
+```
+
+Diagnostics are also published asynchronously after `text/open` and `text/change`:
+
+```json
+{"event":"diagnostics/publish","params":{"path":"/home/me/project/src/main/kotlin/App.kt","version":7,"diagnostics":[]}}
+```
+
+## Current Methods
+
+The `kotlin/*` names are historical protocol names. Diagnostics and heuristic intelligence currently also handle `.java` files where noted.
+
+- `ping`
+- `workspace/open`
+- `workspace/close`
+- `text/open`
+- `text/change`
+- `text/close`
+- `kotlin/diagnostics`
+- `kotlin/completion`
+- `kotlin/definition`
+- `kotlin/references`
+- `kotlin/rename`
+- `kotlin/hover`
+- `gradle/tasks`
+- `gradle/run`
+
+## `workspace/open` Result
+
+Module `sourceRoots` and `testSourceRoots` include Gradle IdeaModel roots plus common generated Kotlin/Java source directories under `build/generated/` when those directories already exist.
+
+```json
+{
+  "root": "/home/me/project",
+  "gradle": true,
+  "modules": [
+    {
+      "name": "app",
+      "gradlePath": ":app",
+      "directory": "/home/me/project/app",
+      "sourceRoots": [],
+      "testSourceRoots": [],
+      "resourceRoots": [],
+      "testResourceRoots": []
+    }
+  ],
+  "sourceRoots": [],
+  "tasks": []
+}
+```
+
+## `gradle/run` Request
+
+```json
+{"id":2,"method":"gradle/run","params":{"task":":app:test"}}
+```
+
+## `kotlin/diagnostics` Request
+
+Supports Kotlin and Java files. Kotlin diagnostics use the embedded Kotlin compiler; Java diagnostics use the JDK compiler. Main files use main source roots, while test files use main plus test source roots. Existing module output directories under `build/classes/` and `build/resources/` are added to the compiler classpath.
+
+```json
+{"id":3,"method":"kotlin/diagnostics","params":{"path":"/home/me/project/src/main/kotlin/App.kt"}}
+```
+
+## `kotlin/diagnostics` Result
+
+```json
+{
+  "diagnostics": [
+    {
+      "severity": "error",
+      "message": "Syntax error",
+      "path": "/home/me/project/src/main/kotlin/App.kt",
+      "line": 1,
+      "column": 12
+    }
+  ]
+}
+```
+
+## `kotlin/completion` Request
+
+Returns prefix-filtered Kotlin/Java keywords plus heuristic declarations and identifiers from the current buffer and workspace.
+
+```json
+{"id":4,"method":"kotlin/completion","params":{"path":"/home/me/project/src/main/kotlin/App.kt","line":10,"column":8}}
+```
+
+`line` and `column` are 1-based.
+
+## `kotlin/completion` Result
+
+```json
+{
+  "items": [
+    {"label": "fun", "kind": "keyword"}
+  ]
+}
+```
+
+## `kotlin/hover` Request
+
+Returns keyword or heuristic Kotlin/Java declaration information for the identifier at the requested position.
+
+```json
+{"id":5,"method":"kotlin/hover","params":{"path":"/home/me/project/src/main/kotlin/App.kt","line":10,"column":8}}
+```
+
+`line` and `column` are 1-based.
+
+## `kotlin/hover` Result
+
+```json
+{"contents":"Kotlin keyword `fun`"}
+```
+
+`contents` is `null` when no hover information is available.
+
+## `kotlin/definition` Request
+
+Returns heuristic Kotlin/Java declaration locations for the identifier at the requested position.
+
+```json
+{"id":6,"method":"kotlin/definition","params":{"path":"/home/me/project/src/main/kotlin/App.kt","line":10,"column":8}}
+```
+
+`line` and `column` are 1-based.
+
+## `kotlin/definition` Result
+
+```json
+{
+  "locations": [
+    {"path": "/home/me/project/src/main/kotlin/App.kt", "line": 4, "column": 7}
+  ]
+}
+```
+
+## `kotlin/references` Request
+
+Returns heuristic Kotlin/Java text references for the identifier at the requested position.
+
+```json
+{"id":7,"method":"kotlin/references","params":{"path":"/home/me/project/src/main/kotlin/App.kt","line":10,"column":8}}
+```
+
+`line` and `column` are 1-based.
+
+## `kotlin/references` Result
+
+```json
+{
+  "locations": [
+    {"path": "/home/me/project/src/main/kotlin/App.kt", "line": 4, "column": 7}
+  ]
+}
+```
+
+## `kotlin/rename` Request
+
+```json
+{"id":8,"method":"kotlin/rename","params":{"path":"/home/me/project/src/main/kotlin/App.kt","line":10,"column":8,"newName":"newSymbol"}}
+```
+
+This is currently preview-only. It does not modify files.
+`newName` must be a valid identifier and must not be a Kotlin or Java keyword.
+
+## `kotlin/rename` Result
+
+```json
+{
+  "applied": false,
+  "oldName": "oldSymbol",
+  "newName": "newSymbol",
+  "edits": [
+    {"path": "/home/me/project/src/main/kotlin/App.kt", "line": 4, "column": 7, "oldText": "oldSymbol", "newText": "newSymbol"}
+  ]
+}
+```