fix(files): list the git worktree an agent moved into (#765)

Claude Code's EnterWorktree moves the running process into
<repo>/.claude/worktrees/<name>, while Session.workingDir stays on the main
checkout. The Files panel kept walking workingDir, so it listed a tree the
agent had left.

paneCwd already follows the move, measured on Claude Code 2.1.318 in both
directions, so nothing new has to track the agent. It also follows every cd
in a shell, so a new SessionState.liveWorktree narrows it to a linked
worktree, read from the .git file without starting git.

Only a folder strictly below workingDir is ever an answer, and the listing
only starts there: returned paths stay relative to workingDir, so the
preview, raw and edit routes are unchanged and confinement does not widen.
A worktree outside the session folder stays unfollowed.

The panel asks with root=live, shows a strip naming the worktree with a
switch to the session folder, and follows the agent in and out while open.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/wiki/Git-Worktrees.md

@@ -39,6 +39,19 @@ name.
 
 **Open** on a worktree's row starts another session in it, with the CLI chosen above.
 
+## When an agent moves into a worktree
+
+Claude Code can move a running session into a worktree part way through (its EnterWorktree tool),
+and the session's tab stays on the case. While the session's pane is in a worktree inside the
+session's folder, the **Files** panel lists that worktree, so you see the files the agent is
+editing. A strip under the panel's title names the worktree, and its **Session folder** button
+switches to the session's own folder (**Back to worktree** returns). The panel follows the agent
+in and back out on its own while it is open.
+
+A worktree outside the session's folder (`git worktree add ../feature`) is not followed: Codeman
+only serves files inside the session's folder. Open such a worktree as a case of its own with
+Add Case > Link Existing.
+
 ## Removing one
 
 Two ways, and both use `git worktree remove` **without** `--force`:

docs/wiki/Working-With-Files.md

@@ -6,8 +6,9 @@ until you get home.
 
 ## The File Viewer
 
-A panel that browses the active session's working directory. Its header button is on by
-default; if it is missing, re-enable it in **App Settings → Header & Panels**.
+A panel that browses the active session's working directory, or the git worktree its agent
+moved into ([Git Worktrees](Git-Worktrees#when-an-agent-moves-into-a-worktree)). Its header
+button is on by default; if it is missing, re-enable it in **App Settings → Header & Panels**.
 
 It renders what it can: