Separate host-independent helpers under common/core and colocate feature
support code with its owners. Update imports, tests, and source-layout
guidance while preserving runtime behaviour.
PluginDataExDisplayV2.mtime applied `~~` to the sum of millisecond
timestamps before dividing, which keeps only the low 32 bits. The
freshness chip and "Select All Shiny" then compared wrapped values and
could offer an older copy as newer.
Fixes#1194
vorotamoroz