Branch picker action hints

Scenario

Open a trusted git workspace in the Web Shell (qwen serve + the sidebar). Click the branch chip on the workspace folder header (or the composer chip / Environment panel row) to open the branch picker. Exercise the repo through these states between opens:

Tracking origin/main, in sync, clean tree.
git reset --hard HEAD~3 (behind 3, clean).
Same as 2 plus an edited tracked file and one new untracked file.
git checkout -b feat/no-upstream with one local commit (no upstream).
Start a conflicting git rebase and leave it in progress.
git checkout --detach.
Start a conflicting git merge on a branch with one commit ahead.
Push a branch with -u, delete it on the remote, git fetch --prune.

Checks

State 1: Update Project shows "Up to date", Push shows "Nothing to push", Commit shows "No changes"; all three rows are dimmed but still enabled.
State 2: Update Project shows "↓3 · origin/main" in the neutral tone.
State 3: Update Project shows "↓3 · uncommitted changes" in the warning tone and stays enabled; Commit shows "2 changes (1 untracked)" (entries, not files: a partially staged file counts twice).
State 4: Update Project shows "No upstream" and is disabled; Push shows "Sets upstream on push" and is enabled.
State 5: Update Project and Push both show "Rebasing" in the warning tone and are disabled (a rebase detaches HEAD); Commit stays enabled.
State 6: Update Project and Push both show "Detached HEAD" and are disabled.
State 7: Update Project shows "Merging" and is disabled; Push shows "Merging" in the warning tone but stays enabled (a push does not consult the index).
State 8: Update Project shows "Upstream gone" and is disabled; Push shows "Sets upstream on push".
After committing through the Commit dialog and reopening the picker from any of the three entry points (sidebar chip, composer chip, Environment panel), the Commit hint reflects the new tree without waiting for the poll.
With the picker open, run git branch --unset-upstream in a terminal and refocus the window: once the chip's status updates, Update Project flips to disabled "No upstream" without reopening.
Switching the UI language to 中文 renders the localized copy ("已是最新", "无上游分支", "↓3 · 有未提交更改", "2 处更改（1 未跟踪）").

Evidence

Unit coverage lives in packages/web-shell/client/components/BranchPickerPopover.test.tsx (deriveActionHints decision table + rendered disabled/tone assertions) and the open-time status refresh in packages/web-shell/client/components/sidebar/WorkspaceSection.test.tsx.

cd packages/web-shell && npx vitest run \
  client/components/BranchPickerPopover.test.tsx \
  client/components/sidebar/WorkspaceSection.test.tsx \
  client/components/panels/EnvironmentPanel.test.tsx