feat: rename info to status, add /status slash command

Rename session info endpoint from /sessions/:id/info to /sessions/:id/status
and update frontend tab label accordingly. Add /status slash command that
displays current session metrics (message count, context usage, cache hit
rate, used skills) as formatted text in any channel.

spec/docs.go

@@ -4395,7 +4395,7 @@ const docTemplate = `{
                 }
             }
         },
-        "/bots/{bot_id}/sessions/{session_id}/info": {
+        "/bots/{bot_id}/sessions/{session_id}/status": {
             "get": {
                 "description": "Get aggregated info for a chat session including message count, context usage, cache stats, and used skills",
                 "tags": [