v0.4.10

Four separate acts, and the ones that were missing

A client watching a shell could take it over but never give it back, and the
button that said 关闭标签页 ended the process instead. Both are fixed, and the
four things a client can do to a shell are now four buttons on both clients.

• 释放控制权 exists. The release frame was in the protocol and no client
  ever sent it. A client holding the lease is offered 释放 in the header and in
  the banner; pressing it gives the lease up, leaves the process running and
  leaves the tab watching it. The hub hands the lease to the machine the shell
  runs on, so the shell is not left mute.
• The hub was throwing a release away. handleRelease dropped the lease and
  then asked giveAway to hand it to the machine's own window — which is the
  client that had just released it, because drop had just added it to the
  watchers. A release from the machine's own window was a no-op, and that
  window is the one that releases most, since it holds its own shells by
  default.
• The 会话 panel's × closed the tab and ended the shell. It was wired to the
  same act as 结束, so "close this tab" killed a process on a machine somewhere
  — for every client watching it, not only the window that clicked. It closes
  the tab now, and 结束 has its own button on the row of the shell it ends.
• A tab whose shell exited is no longer removed. The tab is where the
  shell's last output is read, so ending a session is not a reason to lose it.
  The browser client already behaved this way; the desktop app's reconcile did
  not.
• The desktop app catches up with the browser client's layout. It gains the
  tab strip, the command composer with its history bar, and the 280px session
  inspector, and its sidebar and terminal take the same measurements the
  browser client uses. Without a composer the window had no way to send Esc,
  Tab, Ctrl or an arrow key at all, because a terminal is a display surface and
  cannot produce them.
• The app icon is transparent. resources/icon.png had an opaque dark plate
  composited behind the logo, which is what put a dark square in the macOS Dock
  and the Windows taskbar. Every icon is rendered from the one transparent
  source now, and a test reads the pixels so it cannot come back.
• The release pipeline builds the frontend. The cli job never ran
  build:web, so every CLI artifact published so far shipped without the
  browser client embedded — tfd answered the browser with nothing.
• The macOS firewall prompt is explained before it appears. The 本机服务
  switch says that the system asks once about incoming connections and that
  clicking 允许 settles it for good. A service that failed to start is stated in
  the status bar rather than only logged, and the background update check starts
  off instead of calling out on every launch.