Fix multiple bugs: XSS vulnerabilities, operator precedence, event listener loss, race condition

[hobostay]

Summary

• Fix XSS in browserViewManager.ts: Three locations directly interpolated URLs and error descriptions into document.body.innerHTML via executeJavaScript without escaping. Malicious URLs containing <script> tags or HTML entities could execute arbitrary JavaScript in the Electron renderer. Fixed by HTML-escaping all interpolated values before use.

• Fix operator precedence bug in videoActionHandler.ts: The expression "text" + statusData.failure_reason ?? "" evaluates as ("text" + statusData.failure_reason) ?? "" because + has higher precedence than ??. This makes the nullish coalescing operator dead code — when failure_reason is undefined, the string "undefined" is displayed instead of an empty string. Added parentheses: (statusData.failure_reason ?? "").

• Fix unhandled promise rejection in setContent.ts: The Promise.all(promises).then(...) for loading CSS into iframes has no .catch() handler. If any CSS fetch fails, the iframe never gets srcdoc content at all. Added a .catch() that renders the message content even without CSS.

• Fix event listener loss in setContent.ts: contentElm.innerHTML += contentHtml serializes and re-parses the entire DOM, destroying all existing event listeners on child elements (including previously-attached link click handlers). Replaced with insertAdjacentHTML("beforeend") which preserves existing DOM nodes.

• Fix race condition in webSocketAPI.ts: The onclose handler unconditionally calls createWebSocket() when autoReconnect is true. If the socket closes rapidly multiple times (e.g., network flapping), multiple concurrent reconnection attempts are spawned, potentially creating duplicate WebSocket connections. Added a reconnecting flag to serialize reconnection attempts.

Test plan

• Verify browser tabs still show error pages correctly when URLs fail to load
• Verify video agent displays failure reason correctly when failure_reason is undefined vs set
• Verify iframe content renders even when CSS fetch fails
• Verify link click handlers still work after multiple messages are appended in chat
• Verify WebSocket reconnects properly after connection loss without creating duplicates

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