if (cmd === "copy_stream_to_folder") {
        /* the real command copies only what the stream cache already holds */
        let saved = 0, missing = 0;
        for (const f of args?.files || []) { if (cacheReady.has(f.path)) saved++; else missing++; }
        return Promise.resolve([saved, missing]);
    }
    if (cmd === "play_row_count") return Promise.resolve(4210);
    if (cmd === "debug_stats") {
        /* the overlay's shape, camelCase as serde renames it; the numbers
           wander a little so the screen is seen to be live */
        const t = Date.now() / 1000;
        return Promise.resolve({
            cpuProcess: 7.5 + Math.sin(t), cpuSystem: 22 + Math.cos(t) * 3,
            gpuPercent: null, gpuAppPercent: null,
            memWorkingSet: 431_000_000, memPrivate: 0,
            memSystemUsed: 5_400_000_000, memSystemTotal: 7_900_000_000,
            netRxBps: 1_250_000, netTxBps: 96_000,
            processCount: 3, uptimeSecs: 742,
            dlReceived: xfer ? Math.round(xfer.received) : null,
            dlTotal: xfer ? xfer.total : null,
            dlDone: xfer ? xfer.received >= xfer.total : null,
            normalizationEnabled: mockSettings.volume_normalization !== false, targetLufs: -14,
            loudness: { lufs: -9.8, peak: 0.98, gainDb: -4.2, cached: true, analyzing: false, source: "cache", headStartDb: 0, prefixGainDb: null },
            mainFadeGain: 1, normNowDb: -4.2, normTargetDb: -4.2,
            previewVolume: null, previewNormDb: null,
            preloadDl: [{ username: "dusty_crates", path: "Music\\Daft Punk\\Discovery\\02 Aerodynamic.flac", state: "transferring", place: null, received: 5_000_000, total: 12_000_000, speedBps: 850_000 }],
        });
    }