fix: sync Twitter cookies to xreach session.json on configure

When running 'agent-reach configure twitter-cookies', credentials are now
automatically written to ~/.config/xfetch/session.json so that 'xreach auth
check' works without manual intervention.

Preserves existing session.json fields if the file already exists.
Falls back gracefully if the sync fails (still saves to agent-reach config).

Fixes #50

agent_reach/cli.py

@@ -704,7 +704,25 @@ def _cmd_configure(args):
         if auth_token and ct0:
             config.set("twitter_auth_token", auth_token)
             config.set("twitter_ct0", ct0)
-            print(f"✅ Twitter cookies configured!")
+
+            # Sync credentials to xreach's session.json so xreach auth check works
+            try:
+                import json
+                xfetch_dir = os.path.join(os.path.expanduser("~"), ".config", "xfetch")
+                os.makedirs(xfetch_dir, exist_ok=True)
+                session_path = os.path.join(xfetch_dir, "session.json")
+                session_data = {}
+                if os.path.exists(session_path):
+                    with open(session_path, "r", encoding="utf-8") as sf:
+                        session_data = json.load(sf)
+                session_data["authToken"] = auth_token
+                session_data["ct0"] = ct0
+                with open(session_path, "w", encoding="utf-8") as sf:
+                    json.dump(session_data, sf, indent=2)
+                print("✅ Twitter cookies configured (synced to xreach)!")
+            except Exception as e:
+                print("✅ Twitter cookies configured!")
+                print(f"⚠️ Could not sync to xreach session.json: {e}")
 
             print("Testing Twitter access...", end=" ")
             try: