feat: MCP-client federation surface (v0.12.0)

Picks up the four new HubAdmin RPCs that drive Studio's
MCP-clients editor:

- `listMcpClients()` — config + last-discovery snapshot.
- `refreshMcpClients()` — re-run discovery against the live
  daemon.
- `addMcpClient(name, endpoint, apiKeyEnv?, description?)` —
  persist + refresh in one round-trip.
- `removeMcpClient(name)` — drop persisted entry and live
  synthetic capabilities.

Typedefs for `ListMcpClientsResponse`, `McpClientStatus`,
`McpClientConfigEntry` so callers don't import generated/.

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

pubspec.yaml

@@ -1,6 +1,6 @@
 name: fai_dart_sdk
 description: gRPC client SDK for the F∆I Platform hub. Used by F∆I Studio and Tier-3 domain apps.
-version: 0.11.0
+version: 0.12.0
 publish_to: 'none'
 repository: https://git.flemming.ws/fai/dart-sdk