Several pages still forced a single environment where the header selection
should decide: keybindings, the text generation and source control writer
model pickers, the Devices section's own environment picker, and the project
Overview page which duplicated the Actions editor. Keybindings now write to
every selected environment; model pickers validate the choice against every
target and fan out; Devices follows the header select; Providers and
Diagnostics, which are per machine, explain that in their own words; the
Project page keeps identity, checkouts, merge method and danger only, with
the t3.json import moved to Actions. Appearance and SnapShots hide the scope
selects since every row there is device-local. Each server row's caption now
opens the top-down chain (project override, environment value, built-in
default) per selected environment, marking the layer that took effect.