refactor(text): extract shared summarization service with tts/note/notification modes

Move server-side summarization out of lib/tts/summarization.js into a shared
lib/text module exposing tts, note and notification modes. TTS and notification
runtimes now delegate to the shared service, note mode is used to distill a
selected excerpt into a short project note. Expose the new endpoint via
/api/text/summarize and route it through the common request middleware.

Client voice/summarize.ts accepts a mode option and points at the new
endpoint with an absolute URL that respects the desktop server origin.
VS Code webview swaps the stubbed tts summarize path for /api/text/summarize
and hardens URL parsing with window.location.href as the base.

packages/vscode/webview/main.tsx

@@ -294,7 +294,7 @@ if (workspaceFolder) {
 
 const normalizeUrl = (input: string | URL) => {
   try {
-    return typeof input === 'string' ? new URL(input, window.location.origin) : new URL(input.toString());
+    return typeof input === 'string' ? new URL(input, window.location.href) : new URL(input.toString(), window.location.href);
   } catch {
     return null;
   }
@@ -523,7 +523,7 @@ const handleLocalApiRequest = async (url: URL, init?: RequestInit) => {
     });
   }
 
-  if ((pathname === '/api/tts/speak' || pathname === '/api/tts/say/speak' || pathname === '/api/tts/summarize') && method === 'POST') {
+  if ((pathname === '/api/tts/speak' || pathname === '/api/tts/say/speak' || pathname === '/api/text/summarize') && method === 'POST') {
     return new Response(JSON.stringify({ error: 'TTS endpoints are not available in VS Code runtime' }), {
       status: 501,
       headers: { 'Content-Type': 'application/json' },