v0.8.3

Park & resume — now per-tab

Ctrl-A d / Ctrl-A a operate on the current tab, not the whole window:

• Ctrl-A d parks just the current tab — its window moves to a hidden holding
  session; your other tabs stay put.
• Ctrl-A a resumes a parked tab into the current window (picker; Ctrl-X
  kills one) — it's added as a new tab, not swapped in over everything.
• Cmd+W / tab-close is untouched — park/resume no longer detaches or switches
  sessions.
• Thanks to @mdaneshyab for reporting this in #3.