feat(studio): MCP-clients editor + federated entry rendering (v0.22.0)

The viral-bridge story now has a UI surface. Settings →
MCP Clients lists every configured server, shows last-
discovery health (green dot + tool count, red dot + error
kind), and offers Add / Remove / Refresh.

Add-server dialog: name (no dots), endpoint, optional
api_key_env, optional notes. On submit the hub persists +
re-runs discovery in one round-trip; the Store fills with
synthetic `mcp.<name>.<tool>` entries the operator can see
immediately.

StoreItem now carries `kind` and `provider`. Federated
entries route through a bridge — no install bundle to
download — and Studio's install button renders accordingly
(via the existing "Not installable" path; the Phase-2
follow-up adds an explicit "Configure bridge" call-to-action).

Settings dialog grew to 520×640 with a SingleChildScrollView
so the additional panels don't crowd. Channel pill, system-AI
panel, MCP-clients panel all coexist without a redesign.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

pubspec.lock

@@ -79,7 +79,7 @@ packages:
       path: "../fai_dart_sdk"
       relative: true
     source: path
-    version: "0.11.0"
+    version: "0.12.1"
   fake_async:
     dependency: transitive
     description: