fix(app): Review pane stays on loading for file tree and changes

Summary

Desktop Review can sit forever on both panes:

• Sidebar: Filter files (筛选文件), then 加载中...
• Preview: Loading changes (正在加载更改…)

This is one shared pending flag, not two independent loaders. Related but not the same as #49260 (non-git directory) and #42964 (eager full diffs making Desktop unresponsive).

Environment

• OS: Windows 10/11
• Client: OpenCode Desktop Review tab (session-ui v2 sidebar + preview)
• Workspace: git repository (not a non-git folder)

Reproduction

1. Open a session in Desktop for a git project.
2. Click Review.
3. Leave the panel open.

Observed: left tree and right diff stay on loading copy with no empty state and no error.

A heavy working tree makes this easy to hit. git status --porcelain --untracked-files=all plus per-untracked git diff --no-index will run against every untracked file. A local Electron unpack directory with thousands of files is enough to keep the request outstanding.

Expected

• Bound the VCS request; if it fails or times out, show an error, not a spinner.
• If there is nothing to review, show the empty state.
• Do not treat isPending as still loading when the query is disabled or never started.

Actual

Both panes key off createSessionReview().ready():

const ready = () => {
  if (mode() === "git" || mode() === "branch") return !vcsQuery.isPending
  return true
}

• Sidebar loading: ReviewPanelSidebar diffsReady fallback (common.loading).
• Preview loading: ReviewPanelEmpty when mode is git/branch and !ready() (session.review.loadingChanges).

vcsQuery has no timeout. ready() ignores isError / fetchStatus. TanStack Query v5 keeps isPending === true when there is no cached data even if enabled is false, so a disabled query (disconnected, missing project.vcs, review not yet wanted) also looks like an in-flight load.

Working-tree diffs then call git status --untracked-files=all and may statUntracked / patchUntracked (git diff --no-index) per ?? path in packages/core/src/plugin/vcs/git.ts. That can run for a long time on large untracked trees, so isPending never clears.

Suggested fix

1. Treat loading as isFetching && !isFetched (or fetchStatus === "fetching"), not raw isPending.
2. Add an error empty state when isError.
3. Cap/timeout GET /api/vcs/diff; skip or bound untracked blobs instead of one git diff --no-index per file.
4. Keep ignored build/unpack dirs out of status (--untracked-files=normal or respect ignore rules strictly).

Start with createSessionReview().ready() and the ReviewPanelSidebar and ReviewPanelEmpty loading paths, then inspect vcsQuery state handling. Trace GET /api/vcs/diff into packages/core/src/plugin/vcs/git.ts, including status, statUntracked, and patchUntracked. Done means disabled, failed, empty, and slow reviews no longer leave either pane stuck on a spinner.