[Jinwoo-H]

Summary

• Split pane in wrong worktree: Hidden (but mounted) worktrees kept their focusedGroupId, so their TerminalPanes registered window-level keydown handlers alongside the visible worktree's. Cmd+D, Cmd+W, etc. fired in all worktrees because stopPropagation doesn't block sibling listeners on the same target.
• Duplicate close dialog: Same root cause — multiple closeActivePane handlers fired, showing the confirmation modal multiple times.
• Auto-recreating tabs on close: The auto-create-first-tab effect couldn't distinguish "worktree just activated with no tabs" from "user closed the last tab", so it spawned a replacement terminal immediately after every close.

Changes

• Terminal.tsx: Pass focusedGroupId={undefined} for hidden worktrees so their TerminalPanes get isActive=false and never register keyboard handlers.
• keyboard-handlers.ts: Upgrade all stopPropagation() → stopImmediatePropagation() as defense-in-depth, so even if multiple handlers are active on window, only the first one processes the event.
• Terminal.tsx: Replace single-value initialTabCreationGuardRef with a Set<string> tracking initialized worktrees. Once a worktree has had tabs, closing all of them won't auto-spawn a replacement.

Test plan

• Open two worktrees, switch between them, then Cmd+D in the active one — split should only appear in the visible worktree
• Split a pane, then Cmd+W — close dialog should appear at most once (only if a process is running)
• Close the last terminal tab (idle shell) — no replacement tab should auto-spawn
• Activate a brand-new worktree with no tabs — first terminal should still auto-create
• Cmd+T still creates new tabs in an empty worktree