fix(terminal): prevent infinite reconnect loop on Windows hosts

[lifu963]

Problem

On Windows hosts, the remote terminal UI flashes "Terminal ID is already in use." in an infinite loop, making the terminal page unusable.

Root cause

The Bun PTY API (Bun.Terminal) is POSIX-only. When the CLI runs on Windows, it immediately emits terminal:error. Two bugs then create an infinite loop:

1. Hub (terminalHandlers.ts): The terminal:error handler forwarded the error to the frontend without removing the terminalId from the registry. The next terminal:create attempt was rejected as a duplicate.

2. Web (terminal.tsx): The component reset connectOnceRef on every error, and the ResizeObserver continuously re-triggered connect() — each attempt hitting the stale registry entry.

Fix

Layer	File	Change
Hub	terminalHandlers.ts	Clean up terminalRegistry on terminal:error (same pattern as terminal:exit)
Web	terminal.tsx	Stop resetting connectOnceRef on error/exit to break the reconnect loop
Web	terminal.tsx	Detect Windows hosts via session metadata; render a static "unsupported" message instead of attempting connection
Web	SessionChat.tsx, HappyComposer.tsx, ComposerButtons.tsx	Disable the Terminal button for Windows hosts with tooltip
Web	terminalSupport.ts	Utility to check session.metadata.os
Web	en.ts, zh-CN.ts	Add terminal.unsupportedWindows i18n key
CLI	TerminalManager.ts	Improve error message wording
Docs	faq.md	Note Windows terminal limitation

Test plan

• Windows host: terminal page shows "Remote terminal is unavailable on Windows hosts." (no flash)
• Windows host: Terminal button in composer is disabled with tooltip
• Linux/macOS host: terminal still connects and works normally (not tested — no POSIX host available)
• Unit tests pass for terminalSupport helpers
• Unit test verifies terminalRegistry.remove() is called on terminal:error

Made with Cursor

[github-actions]

Findings

• None.

Summary
Review mode: initial. No issues found in changed lines. Residual risk: Linux/macOS terminal path not validated in this review.

Testing

• Not run (automation)

HAPI Bot