Run the wizard checks and task runners in isolated python mode (-I)

coordinator/internal/agent/check.go

@@ -89,9 +89,11 @@ func CheckEnvironment(ctx context.Context) CheckReport {
 func CheckEnvironmentWithPython(ctx context.Context, python string) CheckReport {
 	report := CheckReport{Agent: Version, Python: CheckItem{Name: "python", OK: true, Detail: python}}
 	// The version comes from importlib.metadata, so the wizard can compare the
-	// installed package with the binary version and offer an upgrade.
+	// installed package with the binary version and offer an upgrade. -I keeps
+	// the working directory out of sys.path, so a scimesh checkout in the
+	// wizard's cwd can never shadow the venv installation.
 	//nolint:gosec // G204: python is a resolved interpreter path, the argument list is constant
-	cmd := exec.CommandContext(ctx, python, "-c", "import importlib.metadata as m; print(m.version('scimesh'))")
+	cmd := exec.CommandContext(ctx, python, "-I", "-c", "import importlib.metadata as m; print(m.version('scimesh'))")
 	out, err := cmd.Output()
 	if err != nil {
 		// The worker executes workloads by spawning scimesh's task runner, so