feat(shell): refactor shell nav and unify worktree workspace actions by wsp1911 · Pull Request #233 · GCWing/BitFun

@wsp1911

@wsp1911

- replace Terminal Hub with a source-aware shell nav for manual and agent terminals
- persist user-defined terminal profiles and support quick creation with non-default shells
- move worktree actions into workspace management, with open-on-create and linked worktree deletion