Declare the guest grants that already shipped

Inverting the grantable rule from the .view suffix to explicit declaration
dropped every permission that had qualified by how it was spelled. Two of
them were shipped guest features with grants already in the field.

guides.view: the nav item and list_guides both reason in comments about a
signed-out reader holding it, and the route is written around one - drafts
are filtered out, search matches the published revision so draft wording
cannot leak through a hit, and the author branches cannot open for a caller
with no user id.

tools.view: without it a guest holding tools.secrets has permission to use
Secure Send and no way to reach the page, because tools.view is what puts
the entry in the nav. The tools themselves run in the browser and touch no
data.

The failure was worse than a missing checkbox. update_role refuses the
WHOLE request when any submitted permission is undeclared, and the role
grid resubmits what the role already holds, so a site that granted either
of these under the old rule could no longer save the guest role at all -
including to tick assets.view, which is the grant the shop floor needs to
look up an asset number without signing in.

The test asserts both stay grantable, so narrowing the set again means
looking at what is already granted in the field rather than only at what
the catalogue declares.

Scope: product

plugins/guides/plugin.py

@@ -74,6 +74,25 @@ class GuidesPlugin(BasePlugin):
             ('guides.delete', 'Delete guides', 'guides'),
         ]
 
+    def get_guest_grantable_permissions(self) -> List[str]:
+        """A procedure is for whoever is standing at the machine.
+
+        Guides are written to be followed on the floor, by people who often
+        have no account and no reason to get one. The nav item and the API
+        route both already reason about a signed-out reader holding this, so
+        the grant was intended from the start; it qualified under the old
+        .view suffix rule and is written down here now that a grant has to be
+        declared.
+
+        What it reaches is bounded by the routes, not by this: list_guides
+        returns published guides only, matching search against the PUBLISHED
+        revision so draft wording cannot leak through a hit, and a guest can
+        never take the author branches because a guest has no user id. Guide
+        history stays with the editors. Publishing, editing and deleting are
+        separate permissions and none of them is grantable.
+        """
+        return ['guides.view']
+
     def get_navigation_items(self) -> List[Dict]:
         # Position 8, directly under Slides (7), rather than down in the
         # Information section with the reference lists. A guide is something you