feat: update Deno installation to use shell script only

- Simplify ensure_installed method to use only the official shell script
- Remove fallback installation methods for cleaner implementation
- Use curl -fsSL https://deno.land/install.sh | sh for installation

Author: observerw

src/lsp_client/clients/deno/client.py

@@ -155,11 +155,14 @@ async def ensure_installed(self) -> None:
         logger.warning("deno not found, attempting to install...")
 
         try:
-            await anyio.run_process(["npm", "install", "-g", "deno"])
-            logger.info("Successfully installed deno via npm")
+            await anyio.run_process(
+                ["sh", "-c", "curl -fsSL https://deno.land/install.sh | sh"]
+            )
+            logger.info("Successfully installed deno via shell script")
             return
         except CalledProcessError as e:
             raise RuntimeError(
-                "Could not install deno. Please install it manually with 'npm install -g deno'. "
+                "Could not install deno. Please install it manually with:\n"
+                "curl -fsSL https://deno.land/install.sh | sh\n\n"
                 "See https://deno.land/ for more information."
             ) from e