[eric] fix MCP empty responses + diagnose Twitter payment issue

Root cause of "(empty response)" for Reddit MCP:
- Reddit MCP returns valid JSON (posts with titles, scores, etc.)
- agent_loop.py truncated display text to 2000 chars
- Truncated JSON breaks JSON.parse in frontend ToolCallBubble
- Frontend falls through to data: {} → renders "(empty response)"
- Increased display limit to 15000 chars (matches BrowserGetText)

Twitter/xbird MCP:
- Returns "402 Payment Required" — xbird needs paid credits
- Not an OpenSwarm bug, tool itself requires payment

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/apps/agents/agent_loop.py

@@ -314,7 +314,7 @@ class AgentLoop:
             result_msg = Message(
                 role="tool_result",
                 content={
-                    "text": result_text[:2000] if result_text else "Done.",
+                    "text": result_text[:15000] if result_text else "Done.",
                     "tool_name": tc.name,
                     "elapsed_ms": elapsed_ms,
                 },

electron/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "openswarm",
-  "version": "1.0.9",
+  "version": "1.0.10",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "openswarm",
-      "version": "1.0.9",
+      "version": "1.0.10",
       "hasInstallScript": true,
       "dependencies": {
         "electron-updater": "^6.3.0",