projects: return the invite kind in GET /api/projects/{id}/invites (prerequisite for #2067, not the UI) (#2973)

* Surface pending invites in Members screen + Agents app (issue #2067)

Docs-Reviewed: executor rescue commit -- the model left these edits uncommitted and wrote no commit message, so doc drift was NOT assessed by the model; the lead reviews docs at PR time.

* changelog: fragment for the invite kind field added to the invite list payload

Author: jaylfc

changelog.d/tsk-mj5blg-invite-kind.md

@@ -0,0 +1,3 @@
+### Added
+
+- `GET /api/projects/{id}/invites` now returns each invite's `kind` (`agent` or `collab`), so the Members and Agents screens can badge pending invites by type

tinyagentos/routes/project_invites.py

@@ -737,6 +737,7 @@ async def list_invites(
             "status": i["status"],
             "expires_ts": i["expires_ts"],
             "redeemed_by": i.get("redeemed_by"),
+            "kind": i.get("kind", "agent"),
         }
         for i in items
     ]