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/src/server.js

@@ -2,7 +2,6 @@ import express from "express";
 import crypto from "node:crypto";
 import { postPRComment } from "./gitea.js";
 import { reviewPullRequest } from "./runner.js";
-import { startMatrixBot } from "./matrixBot.js";
 
 const app = express();
 app.use(
@@ -60,7 +59,3 @@ app.post("/webhooks/gitea", async (req, res) => {
 app.listen(PORT, () => {
   console.log(`claude-agent listening on :${PORT}`);
 });
-
-startMatrixBot().catch((err) => {
-  console.error("matrix bot failed to start:", err);
-});