EnterWorktree now stays inside the folders allowed at launch

A worktree is a separate working copy of a git repository, which Claude creates and enters with the EnterWorktree tool. When permissions.blockFileToolReadsOutsideWorkingDirectories is on, EnterWorktree now checks the target against the folders the session was launched with:

• It refuses to create, enter or move into a worktree outside those folders.
• If a check fails after the move, it returns the session to its previous folder.
• After such a return, the error says where the session now is.

Previously the only check was the permission prompt asking to enter the worktree.