Sync types and operations with backend for social auth and agent assignments

Adds SocialAuthProvider, AgentAssignment types, and integration compat test.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

types.go

@@ -253,6 +253,14 @@ type IssueApiTokenRequest struct {
 type IssueApiTokenResponse struct {
 	Token     string `json:"token"`
 	ExpiresAt *int64 `json:"expires_at"`
+	TokenID   string `json:"token_id"`
+}
+
+type RotateApiTokenResponse struct {
+	Token                  string `json:"token"`
+	ExpiresAt              *int64 `json:"expires_at"`
+	TokenID                string `json:"token_id"`
+	PreviousTokenGraceUntil int64 `json:"previous_token_grace_until"`
 }
 
 type HealthResponse struct {