generate_model_with_provider

        The cloud, provider-backed creation path: hands a natural-language
        description to an external idea-to-3D service, audits the candidate
        for printability and design correctness, and can perform one or
        more corrective retries using feedback from failed attempts.

        This is NOT the default. It needs a configured provider (the user
        supplies their own API key). For most custom objects the free,
        keyless path is to author the OpenSCAD yourself and compile it with
        ``compile_scad`` — no provider required. Reach for this tool when
        the shape is organic or photo-derived and hard to express in
        OpenSCAD AND a provider is configured.

        For the user-facing saved-goal flow (capturing duty / environment /
        materials / safety so the audit and post-print review can verify
        the result against the user's intent), call this through
        ``design_session(verb="generate", session_id=...)`` rather than
        calling ``generate_model_with_provider`` directly.

        Provider notes:
        - ``auto`` prefers Gemini for idea-to-CAD when available.
        - ``openscad`` is intentionally rejected here because it compiles
          code; it does not turn a natural-language idea into geometry.

        No-provider fallback:
        - If no cloud provider is configured this raises NO_PROVIDER. Do
          NOT ask the user to set an API key — fall back to writing the
          OpenSCAD yourself and compiling it with compile_scad. That free,
          local path is the default for custom objects; cloud providers are
          an opt-in the user supplies their own key for (best for organic
          or photo-based shapes OpenSCAD can't easily reach).

        Args:
            requirements: Natural-language description of the part to create.
            provider: ``auto``, ``gemini``, ``meshy``, ``tripo3d``, or ``stability``.
            material: Optional material target (e.g. ``"petg"``).
            printer_model: Optional printer model ID (e.g. ``"bambu_a1"``).
            style: Optional style hint for providers that support it.
            output_dir: Optional directory for generated files.
            build_volume_x: Optional build volume X override in mm.
            build_volume_y: Optional build volume Y override in mm.
            build_volume_z: Optional build volume Z override in mm.
            nozzle_diameter: Printer nozzle diameter in mm.
            layer_height: Printer layer height in mm.
            max_overhang_angle: Supportless overhang threshold in degrees.
            timeout: Max seconds to wait per generation attempt.
            max_attempts: Max corrective generation attempts.