refactor: remove Discord and Toutiao channels (#234)

Discord only returns server metadata (no messages without Bot Token),
not useful enough. Toutiao search was fragile (HTML scraping). Both
can be revisited when better upstream tools appear.

75 tests passing.

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

.claude/settings.local.json

@@ -0,0 +1,7 @@
+{
+  "permissions": {
+    "allow": [
+      "WebFetch(domain:community.groq.com)"
+    ]
+  }
+}