Restructure chat service, web routes, and add test suite

Split monolithic chat service into modular structure with Matrix client
support, extract web server into per-resource route modules, introduce
bootstrap/main-loop separation, and add comprehensive vitest coverage
across services, repositories, and utilities. Adds project docs and
CLAUDE.md agent instructions.

src/browser/client.ts

@@ -7,6 +7,7 @@ import fs from 'fs';
 export class BrowserClient {
   private context: BrowserContext | null = null;
   private sessionDir: string | null = null;
+  private sessionValidityInFlight: Promise<boolean> | null = null;
 
   constructor(
     private config: Config,
@@ -59,6 +60,16 @@ export class BrowserClient {
   }
 
   async isSessionValid(): Promise<boolean> {
+    if (this.sessionValidityInFlight) {
+      return this.sessionValidityInFlight;
+    }
+    this.sessionValidityInFlight = this.doSessionValidityCheck().finally(() => {
+      this.sessionValidityInFlight = null;
+    });
+    return this.sessionValidityInFlight;
+  }
+
+  private async doSessionValidityCheck(): Promise<boolean> {
     try {
       const page = await this.getPage();
       await page.goto('https://www.reddit.com', { waitUntil: 'domcontentloaded', timeout: 30000 });

src/browser/media-downloader.ts

@@ -1,29 +0,0 @@
-import type { Page } from 'playwright';
-import type { Logger } from '../utils/logger.js';
-import type { MediaDownloadResult, MediaDownloader } from '../services/media.js';
-
-export class PlaywrightMediaDownloader implements MediaDownloader {
-  constructor(
-    private page: Page,
-    private logger: Logger
-  ) {}
-
-  async fetch(url: string): Promise<MediaDownloadResult | null> {
-    try {
-      const response = await this.page.request.get(url, { timeout: 15000 });
-      if (!response.ok()) {
-        this.logger.warn(`Media download failed (${response.status()}): ${url}`);
-        return null;
-      }
-
-      const headers = response.headers();
-      const contentType = headers['content-type'] ?? null;
-      const buffer = Buffer.from(await response.body());
-
-      return { buffer, contentType };
-    } catch (error) {
-      this.logger.warn(`Media download error for ${url}:`, error);
-      return null;
-    }
-  }
-}