Spike Shell 0.6.0

Spike Shell is a terminal, and now that is all it is.

Chat is gone. Not hidden behind a flag, removed: the chat view, the
reviewer/coder convergence loop it was the only entry point to, and the
transcript parser underneath them. Every interaction goes through the PTY,
which is the thing the agent already speaks. ⌘⇧E and the Default view
setting are gone with it.

Renamed. The app is Spike Shell.app with the identifier
com.annamarie.spike-shell. Before this it installed as Spike.app and
collided with anything else by that name.

This release does not update in place. The identifier changed, so an
existing install cannot upgrade to it. Download the dmg and replace the old
app by hand. The old one can simply be dragged to the trash.

Its own state directory. Settings, workspaces, approvals and the action
log now live in ~/.spike-shell (override with $SPIKE_HOME). Previously
this was ~/.spike, which meant sharing state with any other app using that
path. A fresh install starts empty.

Also in this release:

• the published crate compiles from source again (a missing rusqlite
  declaration made cargo build fail on a clean checkout)
• sign-in flows in the in-pane browser complete, and there is a way back out
• the native browser view no longer paints over its own chrome strip, which
  came from a hardcoded height that had drifted from the CSS
• the permissions list groups by family instead of listing every rule as its
  own row