Add message intent classification (edit/info/help) before routing

Introduces a two-LLM-call pipeline: the first call classifies the user's
message intent as "edit", "info", or "help". Edit messages proceed through
the existing routing → edit → propose flow. Info messages get a generated
response about site content from the manifest. Help messages get a
templated capabilities overview. This handles open-ended questions like
"What can I do?" or "What does my site have on it?" which previously
had no path through the system.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/src/sms/templates.ts

@@ -31,4 +31,7 @@ export const SMS_TEMPLATES = {
 
   MMS_NOT_SUPPORTED: () =>
     `Image uploads aren't supported yet. Please describe your change in text.`,
+
+  HELP: () =>
+    `I can help you edit your website via text! Just tell me what to change. Examples:\n- "Change the hero headline to Welcome Home"\n- "Hide the testimonials section"\n- "Add an event: Wine Tasting, June 15, 7pm"\n- "What does my about section say?"\n\nAfter each edit, I'll show you the change and you reply YES to apply or NO to cancel.`,
 } as const;