swarm-wire, swarm-ui: the flow schema lists the values a field takes, and the editor picks them instead of asking for typed names

The schema's event fields gain values, a values_from marker (agents, repos)
and a closed flag; a node field gains the marker and the flag. kind is now
listed as issue and PR, what the router sends. The flow editor shows a
dropdown where the list is complete, suggestions where it is only examples,
and a plain box where there is none.

docs/swarm/notify-router.md

@@ -102,12 +102,21 @@ from the constants the check reads, so an editor offers only what a `PUT`
 accepts:
 
 - `source_events`: `[{name, description}]`, the source events.
-- `fields`: `[{name, description}]`, the condition and recipient fields, and
-  the `{field}` placeholders.
+- `fields`: `[{name, description, values, values_from?, closed}]`, the condition
+  and recipient fields, and the `{field}` placeholders. `values` lists what the
+  field holds, as far as the controller knows, as `{name, description}` pairs, such as the `issue` and
+  `PR` of `kind`.
 - `node_kinds`: `[{kind, description, fields}]` for `source`, `match`, `todo`
-  and `request_reviewer`; each field is `{name, description, required, values}`, and `values`
+  and `request_reviewer`; each field is
+  `{name, description, required, values, values_from?, closed}`, and `values`
   lists the accepted `{name, description}` pairs (the `upsert` and `clear` of a
   todo's `op`), empty for other fields.
+- `values_from` on a field says where an editor asks for values that are only
+  known live: `agents` is the names `GET /api/agents` lists, `repos` the ones
+  `GET /api/repos` lists. `closed` says `values` and that source are every value
+  the field takes, which an editor can show as a dropdown. When false, they
+  are suggestions: the field still takes any other text, such as an `action` the
+  forge adds later or the login of a reviewer who is no agent.
 - `limits`: `{max_nodes, max_depth, max_flows}`.
 
 A controller that predates `schema` leaves it out of the answer; a client reads