v0.2.4

fix(v0.2.4): don't quit app when prompt window closes during bootstrap

v0.2.3 logs from a successful prompt showed:

  [+22.93s] [health] polling http://localhost:8787/health
  [+22.96s] [prompt] window closed (resolved=true)
  [+22.97s] [ssh] exited code=null signal=SIGTERM   ← SSH killed!

Between the prompt closing and the main BrowserWindow opening (which
waits for /health), there is a moment with zero windows. That fires
app.on('window-all-closed'), and our handler treats it as "user
closed the app" — SIGTERMs SSH and quits.

Add a bootstrapDone flag set after createWindow returns. The handler
returns early until then.