fix(browse): make connect --supervise actually respawn a crashed server

The supervisor respawned with a block-scoped env that no longer existed, so
every attempt threw and the loop gave up after five tries. The headed env is
now one pure helper used by connect and respawn, the loop is an injectable
runHeadedSupervisor with behavioral tests, failures name the daemon log and
relaunch command, and connect's usage advertises --supervise.

browse/sections/command-list.md

@@ -163,7 +163,7 @@ Refs are invalidated on navigation — run `snapshot` again after `goto`.
 ### Server
 | Command | Description |
 |---------|-------------|
-| `connect` | Launch headed Chromium with Chrome extension |
+| `connect [--supervise]` | Launch headed Chromium with Chrome extension; --supervise keeps the CLI attached and respawns a crashed server |
 | `disconnect` | Disconnect headed browser, return to headless mode |
 | `focus [@ref]` | Bring headed browser window to foreground (macOS) |
 | `handoff [message]` | Open visible Chrome at current page for user takeover |