optimize: enhance web_search, web_fetch, browser tools

- browser.ts: Fix XSS injection in browserClick/browserType via JSON.stringify
- browser.ts: Replace fixed 1000ms wait with did-finish-load event + 30s timeout
- web_fetch: Add 15s HTTP timeout via AbortController
- web_fetch: Improve HTML→text conversion (block-level tags→newlines, nav/header/footer removal, comprehensive HTML entity decoding)
- web_fetch: Add content-length pre-check (10MB limit)
- web_search: Add 15s HTTP timeout per engine request
- web_search: Add URL deduplication across results
- web_search: Clean residual HTML tags/entities from snippets
- download_file: Add 60s download timeout
- tool-registry: Fix missing logWarn import
- Extract shared decodeHTMLEntities with 40+ entity mappings

src/renderer/services/tool-registry.ts

@@ -4,7 +4,7 @@
  */
 
 import type { ToolDefinition, ToolResult } from '../types.js';
-import { logToolStart, logToolResult, logError, logInfo } from './log-service.js';
+import { logToolStart, logToolResult, logError, logInfo, logWarn } from './log-service.js';
 import { getMCPToolDefinitions } from './mcp-client.js';
 
 export const TOOL_DEFINITIONS: ToolDefinition[] = [