feat(fleet): onboarding-injection — comms cheat-sheet + peer roster per agent (#621)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

packages/mosaic/framework/fleet/roster.schema.json

@@ -81,6 +81,18 @@
           "class": {
             "type": "string"
           },
+          "host": {
+            "description": "Host the agent runs on (hostname or IP). Absent = the fleet host. Used by onboarding-injection to render cross-host comms addresses. Manual cross-host listing is a pre-federation stopgap; federation (W1) auto-discovers later.",
+            "type": "string"
+          },
+          "ssh": {
+            "description": "SSH target (user@host) for a cross-host peer, so onboarding renders the `agent-send.sh -H <user@host>` form. Optional; only needed for agents on a different host than the fleet.",
+            "type": "string"
+          },
+          "socket": {
+            "description": "tmux socket the agent's session runs on. Onboarding renders `-L <socket>` when set; absent = the default socket (no `-L`). Must match the LIVE socket, not blindly inherit the roster's tmux.socket_name.",
+            "type": "string"
+          },
           "working_directory": {
             "type": "string"
           },