Remove claude-agent's Matrix presence entirely — Hermes is the only agent in Matrix

By request: one agent in Matrix, not several. Removes matrixBot.js,
router.js (chat-vs-code-task classifier), litellm.js (claude-agent's own
LiteLLM client), the matrix-bot-sdk dependency, runChatTask() and its
gitea.js branch/PR helpers (createBranch/createPullRequest — only ever
called from the now-removed chat flow), and every Matrix/LiteLLM env var
from claude-agent's compose service.

claude-agent already left the control room manually before this merge.
It keeps its Gitea-webhook-triggered PR review, which never touched Matrix
or LiteLLM to begin with.

Makes PR #12 (the claude-bot/Hermes cross-reply cascade fix) moot — the
bug can't happen once claude-agent has no Matrix client at all. Close #12
without merging once this lands.

agent/package.json

@@ -8,7 +8,6 @@
     "start": "node src/server.js"
   },
   "dependencies": {
-    "express": "^4.19.2",
-    "matrix-bot-sdk": "^0.7.1"
+    "express": "^4.19.2"
   }
 }