Add an Entire panel to Orca's right sidebar

Host API 1.0 gives a panel no channel to its worker, but Orca rereads a development folder's panel file when the folder changes. So the worker writes each snapshot (repo status, the branch's trail, recent checkpoints and the connection check) into panel/entire.html, generated from panel/template.html and gitignored. It never writes into an installed copy, which Orca hashes.

The panel refreshes on "Entire: Refresh panel", on "Entire: Check connection" and when an agent finishes, and follows the focused workspace.