`--inspect` refuses every scanner except the fi-8170, blocking the contribution we ask for

[eliseorobles]

Context

CONTRIBUTING.md and README.md both say the single most valuable contribution available is a hardware datapoint: run swift run scandeck-m0 --list and --inspect on your own duplex ADF scanner and report the vendorFeatures dump.

That is currently impossible on any device other than the fi-8170.

ImageCaptureScannerProbe.resolveAndOpenScanner() filters discovered devices through the USB allowlist before opening a session:

// Sources/ScanDeckScanner/ImageCaptureScannerProbe.swift:1302-1303
let candidates = discoveredScanners.filter {
    isSupportedScanner($0) && deviceMatchesSelection($0)
}

isSupportedScanner consults SupportedScanner.usbIdentities, which has exactly two entries (ScannerInventory.swift:23-25). So on any other scanner the probe reports "No supported fi-8170 USB scanner was found."

--list is not gated — it finishes with the full discoveredScanners count and prints name, transport, location and usb=vendor:product. Useful, but not the capability dump the matrix needs.

Why the allowlist exists — do not remove it

Its docstring gives the real reason, and it is a good one: the pipeline depends on duplex, 600 dpi, the configured scan area and the PFU cropping features, and a device missing any of them would produce output that looks plausible and is wrong.

That argument is about scanning, not about looking. --inspect opens a session, dumps capabilities, applies and verifies settings, and closes without scanning. It publishes nothing.

What to change

1. Let --inspect proceed on an unsupported device — make the allowlist filter conditional on the probe's mode. .scan keeps today's behaviour; .inspect accepts any ICScannerDevice. ProbeMode is in Sources/ScanDeckScanner/ScannerProbeConfiguration.swift.
2. Emit a clear unsupported banner before opening: something like "<name> (usb=0x…:0x…) is not a scanner ScanDeck can drive. Inspecting read-only; no scan will run."
3. Leave --scan and the app's pass path exactly as they are. The inventory browser and status monitor must keep reading the same set.
4. Update the failure copy — "No supported fi-8170 USB scanner was found" should not be what an inspection prints once inspection no longer requires support.
5. Update the --inspect usage line in Sources/ScanDeckM0/main.swift.

Expect the capability gates to throw ProbeError.unsupported("duplex scanning") and friends on many devices. That is the datapoint — make sure the failure names which gate failed rather than aborting silently.

How to verify

swift build
swift run scandeck-m0 --list
swift run scandeck-m0 --inspect     # now opens a session on yours
swift test -c release

If you have any ICA-visible scanner, paste the --inspect output into the PR — that is a second contribution for free. If you have none, say so; the change still compiles and the suite still covers the seam. The maintainer will re-verify the fi-8170 path before merge, since that is the one behaviour that must not change.

See CONTRIBUTING.md.