The facet root was the session's working directory and nothing else, so the
only way to scope a conversation to a module was to make the module a
workspace — and the only way to reach anything outside it was `extraRoots`,
which is a fact about the deployment rather than about one conversation.
Scope now has two layers, and the split is the point. The **user layer** is
`config.scopes[sessionId]` — a `focus` and a list of `extras`, written only
from the browser context panel through the settings service, which is what
`settings.mutate` requiring a volatile path buys us. The **agent layer** is in
memory: a narrowing `focus` and its grants. Both can only ever reduce what the
user layer allows, so an agent that goes wrong cannot widen its own scope.
`facet action=focus` is therefore the one scope change the agent may make
unasked, bounded by the scope already in force and decided on canonical targets.
`reset` clears the agent's side only, landing on the user's declaration rather
than on the session directory — landing on the directory would have made
`reset` a widening. `extraRoots` demotes to an optional deployment-wide seed.
The binding now names the context panel as the way to widen, because it is: in
a deployment with no approval channel, `facet action=add` cannot be granted at
all.