recommend_material

        Uses printer DNA + historical data to translate natural language
        intent (e.g. ``"make it strong"``, ``"make it pretty"``,
        ``"make it cheap"``) into an optimal material recommendation
        with settings.

        Pass ``printer_id`` to answer for a SPECIFIC machine — essential
        on a mixed fleet, where "what should I run this in" depends on
        which printer will run it.  The recommendation is then computed
        against that machine's nozzle state (abrasive materials on a
        brass nozzle get an explicit wear warning) and the response
        names the machine it answered for.

        Pass ``on_hand_only=True`` to recommend only from materials you
        physically have — recorded spools (``add_spool``) plus what's
        loaded on your machines (AMS/CFS sync).  Scoped to one printer
        this works on every tier; sweeping a multi-machine fleet in one
        call is a Kiln Business feature (https://kiln3d.com/pricing).  The recommendation's
        ``availability`` block then says WHERE the material is: which
        machine has it loaded, or that it's on the shelf and needs a
        spool swap first.  With ``printer_id`` the loaded half is
        scoped to that one machine (shelf spools always count — they
        can be swapped in); without it, every machine's load counts.
        When nothing on hand suits the request, the response returns
        the best catalog pick clearly labeled needs-purchase — it
        never silently widens to the catalog.  And when what you have
        works but a material you DON'T own fits the job materially
        better, the answer names that too, so "best of what you have"
        is never mistaken for "right for the job".

        **Which material tool to use:**

        - Quick intent-based pick for your own printer? → ``recommend_material`` (this tool)
        - Only from spools I actually own? → ``recommend_material(on_hand_only=True)``
        - Designing a part and need engineering specs? → ``recommend_design_material``
        - Ordering a print from a service? → ``suggest_material_for_order``
        - Which of MY printers has a material loaded? → ``find_printers_with_material``
        - What's loaded across the fleet right now? → ``get_fleet_material_summary``

        Args:
            intent: User intent text (e.g. ``"strong"``, ``"pretty"``).
            has_enclosure: Whether the printer has an enclosure.
            has_heated_bed: Whether the printer has a heated bed.
            budget_usd: Optional maximum budget per kg in USD.
            printer_id: Optional registered printer to answer for.
                Empty = printer-agnostic recommendation.
            on_hand_only: Restrict candidates to recorded inventory
                (loaded materials + shelf spools).  Default False =
                full catalog.