Spike: validate native scanner discovery with ImageCaptureCore

[vincentcr]

Goal
Validate that a small macOS-native helper can discover scanners through ImageCaptureCore and expose the information scanbox needs.

Scope

• Build a minimal Swift command-line helper.
• Enumerate ICScannerDevice instances.
• Emit stable ID, name, model, transport, flatbed/feeder availability, modes, and resolutions.
• Check whether the Xerox on the current LAN appears.
• Do not integrate scanning or change the production CLI yet.

Acceptance criteria

• The helper builds using the macOS Command Line Tools.
• Output is deterministic and machine-readable.
• Zero, one, and multiple device cases exit cleanly.
• Findings and any API limitations are documented.
• No VM is started.

Hardware checkpoint
Run discovery against the Xerox on the current LAN.

[vincentcr]

Checkpoint pushed in d95de7c.

Implemented a small Swift/ImageCaptureCore helper that:

• discovers ICScannerDevice instances without starting the VM;
• emits deterministic JSON with stable identity and transport metadata;
• opens each device and reports flatbed/feeder source capabilities, bit depths, current pixel mode, supported/preferred resolutions, and native resolution;
• records per-device inspection failures in JSON.

Xerox WorkCentre 6605DN native result:

• repeated 5s/15s ImageCaptureCore discovery returned zero scanners;
• Bonjour exposes only _ipp._tcp, with Scan=T and air=none;
• no _uscan._tcp, _uscans._tcp, or _scanner._tcp service was advertised;
• while awake, its eSCL capability endpoint returned HTTP 404;
• WS-Discovery instead identified it as a WSD scan device.

A separate VM follow-up installed sane-airscan 0.99.35 and configured the explicit WSD endpoint because discovery multicast does not cross Lima vzNAT. SANE then found the Xerox, and real 200-dpi grayscale scans succeeded from both ADF and flatbed.

Conclusion: the Xerox is not a native ImageCapture/eSCL device, but it works through sane-airscan's WSD support in the VM. The issue remains open because positive one/multiple-device ImageCapture capability output still needs hardware that macOS exposes in Image Capture.

API limitation documented in native/README.md: ImageCaptureCore exposes current pixelDataType and supported bit depths, but no complete supported-pixel-mode collection.