ledger: complete Solstice XIAO pin release and publish hardware evidence

[te9no]

Summary

Complete Solstice's XIAO ZMK qualifier / unused-peripheral release item.

• Firmware PR Promote verified XIAO pin release and OLED lock-text fix to zmk-0.4 zmk-config-GeaconSolstice#6 merged into zmk-0.4 at 7f64859; its Git tree matches verified source 25dbb3f. Stable main unchanged.
• Source CI 33306076773 and post-merge CI 33306224704 passed all five targets each.
• Publish existing generated-DTS/config and root just.sh evidence, owner's OLED/representative US hardware acceptance, and right CDC boot/readback/recovery/sensor/split evidence.
• Record the associated OLED lock-text integration and CDC recheck; remove the completed Solstice hardware action.

Verification and boundaries

• Ledger: 21 entries validated; 36 Python and 40 dashboard tests passed.
• Scope assertions: only Solstice tracking and its action changed; published Cornix completion/pending follow-up preserved.
• No new flashing or settings reset. No inferred JIS hardware, extended-duration test, or saved-settings error resolution.