[web] Feature request: Files panel (file tree + in-panel preview) for the web portal

Problem

The web portal (kimi web / /web) is great for long sessions, but it has no view of the session's working directory. To confirm a file's content after the agent writes it, I have to leave the browser and switch to a terminal, editor, or Finder, then switch back. This happens dozens of times a day and constantly breaks flow.

Related: #1405 (web users can't see file operation state) — a Files panel would also make file changes visible.

Proposed feature

A Files panel in the right-hand detail panel layer of the chat page:

• File tree of the session working directory, lazily loaded on directory expand
• Find box to filter by filename; entries with git changes get a marker dot
• In-panel file preview, reusing the existing FilePreview component (markdown rendering, code highlighting, images, PDF, CSV, download / open in editor / reveal in Finder)
• Follows portal conventions: right detail-panel layer, Esc to close, auto-reset on session switch, zh/en i18n

Working reference implementation

I have already built and open-sourced this as a patch: https://github.com/baigong-ai/kimi-web-file-explorer

Key points:

• The whole feature is a clean diff of 2 new files + 8 small wiring touches (~665 lines) against apps/kimi-web, built with the same Vite toolchain as upstream
• It only consumes the existing session-scoped server APIs (fs:list / fs:read, with git status) and the existing FilePreview component — no new server routes, no permission changes
• Tested on Kimi Code server 0.31.x and 0.32.0; screenshots are in the repo's docs/

The implementation has been my daily driver for a while and works well.

Questions for maintainers

1. Would you accept this feature upstream?
2. apps/kimi-web no longer exists on main (removed in 0.32.0) but is still on feat/web, and I see kimi-web2 under development. If accepted, which branch should a PR target? I'm happy to port the implementation to kimi-web2 if that's the way forward.

Happy to open the PR once aligned. Thanks!

Start by comparing the existing implementation against apps/kimi-web and the kimi-web2 work, noting that apps/kimi-web was removed from main but remains on feat/web. Read the existing FilePreview component and the session-scoped fs:list and fs:read APIs first. Done means an upstream-compatible Files panel with the described tree, preview, git markers, panel behavior, and zh/en i18n.