Add Haxe language support via vshaxe/haxe-language-server

Includes full setup with ls provider, tests, docs, etc.

docs/01-about/020_programming-languages.md

@@ -63,7 +63,10 @@ Some languages require additional installations or setup steps, as noted.
   (requires local groovy-language-server.jar setup via `GROOVY_LS_JAR_PATH` or configuration)
 * **Haskell**  
   (automatically locates HLS via ghcup, stack, or system PATH; supports Stack and Cabal projects)
-* **HLSL / GLSL / WGSL**  
+* **Haxe**
+  (requires Haxe compiler 3.4.0+ and Node.js; uses the [vshaxe language server](https://github.com/vshaxe/haxe-language-server);
+  automatically downloaded from Open VSX, or discovered from the vshaxe VSCode extension)
+* **HLSL / GLSL / WGSL**
   (uses [shader-language-server](https://github.com/antaalt/shader-sense) (language `hlsl`); automatically downloaded;
   on macOS, requires Rust toolchain for building from source;
   note: reference search is not supported by this language server)

docs/02-usage/050_configuration.md

@@ -484,6 +484,30 @@ Supported settings:
 | `version` | `1.3.0` | Override the bundled version Serena downloads, or builds from source on macOS, when `ls_path` is not set. |
 
 
+#### Haxe
+
+Serena uses the [vshaxe/haxe-language-server](https://github.com/vshaxe/haxe-language-server) for Haxe support.
+Requires Haxe compiler (3.4.0+) and Node.js.
+
+The server is discovered in order: user-configured `ls_path`, system PATH, vshaxe VSCode extension, auto-download from Open VSX.
+
+Supported settings:
+
+| Setting | Default | Description |
+|---|---|---|
+| `ls_path` | auto-discovered | Path to the Haxe language server binary (e.g., `/path/to/server.js`). |
+| `buildFile` | auto-discovered `.hxml` | Relative path to the `.hxml` build file used for compilation (e.g., `build/debug.hxml`). If not set, Serena searches the project for `.hxml` files (max depth 5, skipping dependency directories). |
+| `renameSourceFolders` | not set (LS default) | List of source directories for scoping rename operations (e.g., `["src", "lib"]`). If not set, the Haxe LS uses its own defaults. |
+
+Example (typically in `project.yml`, since these are project-specific):
+
+```yaml
+ls_specific_settings:
+  haxe:
+    buildFile: "build/debug.hxml"
+    renameSourceFolders: ["src", "lib"]
+```
+
 #### Java (`eclipse.jdt.ls`)
 
 The following settings are supported for the Java language server: