fix: worktree hook race + FocusActiveProject keybinding

[neumie]

Summary

• Fix race condition where WorktreeSyncWatcher could remove projects while before_worktree_remove hooks were still running — now checks closing_projects and creating_projects guards
• Add FocusActiveProject toggle keybinding (Cmd+Shift+0 / Ctrl+Shift+0) to zoom into/out of the active terminal's project
• Center-scroll on the previously-focused project when exiting project zoom (deferred to next layout pass for correct bounds)
• Merge new default keybindings into existing saved config on load so new actions appear in the UI
• Revert ShellType::OneShot — all hook terminals go through the session backend

Test plan

• Open multiple projects, focus a terminal, press Cmd+Shift+0 — zooms into that project
• Press Cmd+Shift+0 again — zooms out and centers on the project
• Clear focus via Cmd+0 or status bar ✕ — also centers
• Verify FocusActiveProject appears in keybindings settings panel
• Confirm hooks still run through dtach/tmux/screen session backend
• Create/close worktree projects while hooks are running — no premature removal

🤖 Generated with Claude Code

[matej21]

Nice root cause analysis on both race conditions. The OneShot shell type is a clean solution for bypassing session backend decoupling. A few things to address:

1. ShellType::OneShot appears to be missing from to_command_string() in shell_config.rs — this will likely cause a compile error or exhaustiveness panic. Please add the match arm.
2. The OneShot construction uses -ic flag with $SHELL / /bin/sh fallback. -i is unnecessary for a non-interactive hook command and non-standard with /bin/sh. Consider using just -c.
3. On Windows, $SHELL is unset and /bin/sh doesn't exist. The existing ShellType::for_command handles this with cmd /C — OneShot needs similar platform branching.

[neumie]

Thanks for the review! All three points are moot now — we reverted ShellType::OneShot entirely in d4160f3. Hook terminals now use ShellType::for_command() which already handles all platforms correctly. The actual race condition fix (guarding closing_projects/creating_projects in the sync watcher) stands on its own without needing to bypass the session backend.