Describe snapshot source revisions

docs/spec/08-current-product-backlog.md

@@ -10,53 +10,53 @@ requirements and intended sequencing, not proof of implementation.
 
 ## Project History
 
-- Every listed logical snapshot, including automatic snapshots, must be
+- [x] Every listed logical snapshot, including automatic snapshots, must be
   explicitly restorable from the project history UI.
-- Show which project change produced a snapshot. Prefer immutable revision
+- [x] Show which project change produced a snapshot. Prefer immutable revision
   metadata over storing a second free-form description of the same change.
-- Keep restoration auditable as a new project revision and preserve persistent
+- [x] Keep restoration auditable as a new project revision and preserve persistent
   undo/redo.
 
 ## Distribution Boards
 
-- Assign an optional project floor to a distribution board.
-- Store a supply classification for each distribution board:
+- [x] Assign an optional project floor to a distribution board.
+- [x] Store a supply classification for each distribution board:
   - `AV` (Allgemeine Stromversorgung)
   - `SV` (Sicherheitsstromversorgung)
   - `EV` (Ersatzstromversorgung)
   - `USV` (Unterbrechungsfreie Stromversorgung)
   - `MSR` (Mess-, Steuerungs- und Regelungstechnik)
   - `SiBe` (Sicherheitsbeleuchtung)
-- Let project settings select which catalog supply types are used in a
+- [x] Let project settings select which catalog supply types are used in a
   project. Distribution-board dialogs offer only that selection; a type in
   use cannot be disabled.
-- Include both fields in project snapshots and portable project
+- [x] Include both fields in project snapshots and portable project
   export/import.
-- Persist changes through project commands so they remain undoable after a
+- [x] Persist changes through project commands so they remain undoable after a
   restart.
 
 ## Device Voltage Derivation
 
-- Derive voltage from the selected phase type and the project settings:
+- [x] Derive voltage from the selected phase type and the project settings:
   - single-phase uses the project's single-phase voltage;
   - three-phase uses the project's three-phase voltage.
-- Voltage is not editable on global devices, project devices or circuits.
+- [x] Voltage is not editable on global devices, project devices or circuits.
   Global devices store only their phase; copying one into a project derives
   the target project's voltage.
-- Project-device voltage follows its phase. Circuit voltage follows the
+- [x] Project-device voltage follows its phase. Circuit voltage follows the
   section phase; an unassigned circuit is three-phase only when all assigned
   device rows with a valid phase are three-phase.
-- Changing project voltage settings updates all project devices and circuits
+- [x] Changing project voltage settings updates all project devices and circuits
   atomically in the same persistent Undo/Redo step.
-- Database migration `0019` and snapshot schema version `5` normalize older
+- [x] Database migration `0019` and snapshot schema version `5` normalize older
   stored values. Version-four and older imports remain supported and are
   normalized while being upgraded.
 
 ## Recommended Sequence
 
-1. Distribution-board floor and supply fields.
-2. Device voltage derivation without overrides.
-3. Snapshot-to-revision descriptions and history presentation.
+1. [x] Distribution-board floor and supply fields.
+2. [x] Device voltage derivation without overrides.
+3. [x] Snapshot-to-revision descriptions and history presentation.
 
 The Revit/CSV/IFCGUID round-trip remains a separate jointly planned phase and
 must not be inferred from these tasks.