0.13.0

Added

• A keyboard shortcut cheat sheet, opened by the ? button in the tab bar,
  by Cmd+/ (Ctrl+Shift+/ elsewhere), or from Help → Keyboard Shortcuts. The
  leader key also answers Ctrl+B ?. Every binding the app has was reachable
  only from the README until now, which is the wrong place to look them up from
  inside the app. The list is built per platform, so nobody reads a Cmd row on
  Windows.

• Cerberus now asks before leaving processes behind. Closing a pane kills
  its shell, and with it whatever was running in the foreground — that part has
  always worked. What survives is everything detached from the terminal: a
  nohuped build, a disowned job, a dev server whose launching shell already
  exited. Those used to keep running with nothing left on screen to say so.

  On quit the panes are inventoried before their ptys are killed, and anything
  from that inventory still alive a moment later is listed by name with the
  choice to terminate it or leave it running. A tick box records the answer;
  Settings → Leftover processes on quit changes it back to asking. A process
  that deliberately left its terminal — setsid, a double-forked daemon — is
  not listed, on purpose: it is not the terminal's to kill.

  The Windows path (PowerShell inventory, taskkill /T /F) is implemented and
  unit-tested but, like the rest of the Windows support, has not been exercised
  on real hardware.

Fixed

• The close button of a renamed tab now parks at the right edge of the chip
  instead of sitting against the label.

Full changelog: v0.12.0...v0.13.0