A module's data section says what it keeps and how precious it is; the backup holder's lines,
binding stickiness, retirement on unassign and D13's conditions follow from it, so issue 273's
empty replacement is said and an unassigned module's data is remembered, not forgotten.
ADR 0214 / to-be 43: a node seat whose holder keeps nightly restore points of what every module on
the machine declares. A contribution of kind backup may name its module's own directories, filled
per module when placed. The catalogue check refuses a store provider that contributes no backup;
parsing does not, so the providers already running stay readable.
Each contribution grain was a manifest field and a renderer of its own; a module now contributes
to any seat with a kind that seat receives, the holder places it with
${contribution:<seat>:<kind>}, and the contribution depends on the seat. node-hotkeys is the
first new seat to receive (triggers); the display session receives window-manager config.
jochen
jschoubben