The interactive new-keyboard picker applied the chosen layout with
`hyprctl switchxkblayout <device> <index>`, which flips the *shared*
layout for every keyboard without its own per-device config — so picking
a layout for an external board dragged the built-in keyboard along, and
the change stuck after unplug (it's global state, not device-bound).
Compounding it, the candidate `keyboard.layouts` pool was merged into
`input.kb_layout`, loading those layouts onto the session keyboard too.
Apply the choice as a per-device `hyprctl keyword device[<name>]:kb_layout`
instead — the runtime twin of the declarative `keyboard.devices` blocks —
so it isolates that one keyboard and never touches the built-in board.
Keep the candidate pool out of `input.kb_layout` (session keyboard carries
only `keyboard.layout`); the pool is for external boards, applied per-device.
Also put `nomarchy-keyboard-watch` on PATH when enabled (it was store-path
only via exec-once, so undiscoverable) for debugging.
Found on the Latitude 5410 hardware sweep; picker itself verified working.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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