Promote verified XIAO pin release and OLED lock-text fix to zmk-0.4

[te9no]

Scope

Promote the hardware-verified XIAO pin-release candidate and OLED lock-text fix into zmk-0.4. Stable main is not targeted.

• Disable unused xiao_spi on both halves, preserving the existing ZMK XIAO qualifier, pin assignments and right trackball spi0.
• Hide the overlapping OLED lock-state text; retain Bongo Cat, battery, connection and modifier indicators.

Verification

• Pin-release candidate 643a256: local just.sh 5/5 builds, CI 33037950369, generated DTS/config audit.
• OLED addition: unchanged root just.sh, pristine US/JIS left 2/2 builds; generated DTS identical to pin-release baseline; source config SHA256 a8c051fa7d373105e0d87b356f3589d7b27dbc3ec90f3bee5e43e462570bac7d.
• Owner confirms OLED text removed and other operation normal on left US + right US.
• Right CDC: logs, 1200-baud boot, application readback 1133/1133 blocks, normal return, PMW3610 initialization and split connection passed.

No new flashing or settings reset. JIS hardware and extended-duration acceptance are not claimed. Left saved-settings load errors remain historical observations, not a resolved defect. Unrelated SVG changes are excluded.