fix(sdlc): skip branch push when no origin remote exists

The fatal push+retry logic added in the git flow hardening broke tests
that use local-only git repos without an origin remote. Check for the
origin remote before attempting to push, preserving the fatal behavior
in production (where origin always exists) while allowing local/test
contexts to proceed without a remote.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cmd/sdlc/cmd_branch.go

@@ -52,6 +52,10 @@ var branchCreateCmd = &cobra.Command{
 			}
 		}
 
+		// Only push if origin remote exists (skip in local-only/test contexts)
+		hasOrigin := exec.Command("git", "remote", "get-url", "origin")
+		hasOrigin.Dir = root
+		if hasOrigin.Run() == nil {
 			pushCmd := exec.Command("git", "push", "origin", "HEAD")
 			pushCmd.Dir = root
 			if _, err := pushCmd.CombinedOutput(); err != nil {
@@ -68,6 +72,7 @@ var branchCreateCmd = &cobra.Command{
 						strings.TrimSpace(string(retryOut)), retryErr)
 				}
 			}
+		}
 
 		// Create the git branch
 		branchName := manifest.Name