feat: add Zed extension release artifact with WSL2 support

The Zed extension now detects Windows via current_platform() and
automatically uses `wsl streamd lsp` instead of `streamd lsp`,
enabling seamless LSP support when Zed runs on Windows with streamd
installed in WSL2.

A pre-built zip (extension.toml + extension.wasm) is now built as
`zed-extension-zip` and published to every release. The README gains
a step-by-step WSL2 installation guide.

zed-extension/src/lib.rs

@@ -1,4 +1,4 @@
-use zed_extension_api::{self as zed, Command, LanguageServerId, Result, Worktree};
+use zed_extension_api::{self as zed, Command, LanguageServerId, Os, Result, Worktree, current_platform};
 
 struct StreamdExtension;
 
@@ -12,11 +12,20 @@ impl zed::Extension for StreamdExtension {
         _language_server_id: &LanguageServerId,
         _worktree: &Worktree,
     ) -> Result<Command> {
-        Ok(Command {
-            command: "streamd".into(),
-            args: vec!["lsp".into()],
-            env: vec![],
-        })
+        let (os, _) = current_platform();
+        if os == Os::Windows {
+            Ok(Command {
+                command: "wsl".into(),
+                args: vec!["streamd".into(), "lsp".into()],
+                env: vec![],
+            })
+        } else {
+            Ok(Command {
+                command: "streamd".into(),
+                args: vec!["lsp".into()],
+                env: vec![],
+            })
+        }
     }
 }