fix: show the settings card, and make an edit actually take effect

`mode` and `extraRoots` carried no `volatile()` marker, so the framework's
form projection dropped the whole entry from `settings.describe` and the plugin
had no card under Plugins at all. The marker is what creates the card.

It is also what turns each field into a reference rather than a value: the
resolved config hands `apply` a `{get(), [write]}` per volatile field, which is
how a settings write lands in a running plugin without re-applying it. So the
policy and the guard now read both fields at the point of use instead of
snapshotting them at mount, and `sectionOrder`/`contextOrder` stay unmarked
because a prompt section cannot be re-ordered without a remount.

A section is also registered once as a plain string, so the rule could not
follow a live `mode` without freezing at load. The mode-specific sentence moved
into the binding, which is a callback.

test/scope.test.js

@@ -51,33 +51,47 @@ test('isWideningCall is true only for the one act that needs the user', () => {
 })
 
 test('facetRuleText states the rule and never the binding', () => {
-  const ask = facetRuleText({ mode: 'ask' })
-  assert.match(ask, /put to the user as a question/)
-  // The two modes must not read alike: ask must not claim the call is refused.
-  assert.doesNotMatch(ask, /A call outside it is refused/)
+  const rule = facetRuleText()
 
-  const deny = facetRuleText({ mode: 'deny' })
-  assert.match(deny, /A call outside it is refused/)
+  // Mode-neutral by construction. A prompt section is registered once as a plain
+  // string, and a `volatile()` edit updates the config reference without
+  // re-applying the plugin — so a `mode` interpolated here would freeze at load
+  // while the guard went on enforcing the new one. The mode-specific sentence
+  // lives in the binding, which is a callback.
+  assert.match(rule, /Work inside the facet\./)
+  assert.doesNotMatch(rule, /refused|put to the user as a question/)
+  assert.match(rule, /Never widen the scope on your own initiative/)
 
   // The rule must not name a path: a changing system prompt invalidates the
   // prompt cache for the whole conversation.
-  assert.doesNotMatch(ask, /\/|src\//)
+  assert.doesNotMatch(rule, /\/|src\//)
 
-  assert.equal(facetRuleText({ mode: 'off' }), '')
   assert.equal(facetContextText({ cwd: '/a', root: '/a/b', extras: [], mode: 'off' }), '')
 })
 
 test('facetContextText carries the binding that does change', () => {
+  const ask = facetContextText({ cwd: '/w', root: '/w/src/room', extras: [], mode: 'ask' })
   assert.equal(
-    facetContextText({ cwd: '/w', root: '/w/src/room', extras: [], mode: 'ask' }),
-    'facet: /w/src/room\noutside the facet: ask the user',
+    ask,
+    'facet: /w/src/room\n' +
+      'outside the facet: put to the user as a question — say in one line what you need and why, then record it with `facet action=add` so the rest of the session does not have to ask again',
   )
+
+  const deny = facetContextText({ cwd: '/w', root: '/w/src/room', extras: ['/w/src/shared'], mode: 'deny' })
   assert.equal(
-    facetContextText({ cwd: '/w', root: '/w/src/room', extras: ['/w/src/shared'], mode: 'deny' }),
-    'facet: /w/src/room\ngranted outside it: src/shared\noutside the facet: refused',
+    deny,
+    'facet: /w/src/room\n' +
+      'granted outside it: src/shared\n' +
+      'outside the facet: refused — `facet action=add` asks the user to grant a path, and is the only way to widen the scope',
   )
+
+  // The binding is the only half that can follow a live edit, so the two modes
+  // have to read differently here — they no longer differ in the rule.
+  assert.notEqual(ask, deny)
+
   // Unscoped sessions contribute nothing rather than an empty heading.
   assert.equal(facetContextText({ cwd: '/w', root: undefined, extras: [], mode: 'ask' }), '')
+  assert.equal(facetContextText({ cwd: '/w', root: '/w/src/room', extras: [], mode: 'off' }), '')
 })
 
 test('displayPath prefers the shortest unambiguous form', () => {