Improve error message and add missing Position import to example

Co-authored-by: observerw <[email protected]>

Author: Copilot

examples/tsserver.py

@@ -10,6 +10,7 @@
 
 import anyio
 
+from lsp_client import Position  # noqa: F401 - Used in commented example code
 from lsp_client.clients.tsserver import TsserverClient, TsserverLocalServer
 
 

src/lsp_client/clients/tsserver.py

@@ -98,6 +98,6 @@ async def ensure_installed(self) -> None:
             return
         except CalledProcessError as e:
             raise RuntimeError(
-                "Could not install typescript-language-server. Please install it manually with 'npm install -g typescript-language-server typescript'. "
+                "Could not install typescript-language-server and typescript. Please install them manually with 'npm install -g typescript-language-server typescript'. "
                 "See https://github.com/typescript-language-server/typescript-language-server for more information."
             ) from e