Persist project settings updates

docs/circuit-list-editor-api.md

@@ -62,7 +62,8 @@ The public dispatcher currently supports `circuit.update`, `circuit.insert`,
 `circuit.reorder-section`, `circuit.reorder-sections`,
 `circuit.renumber-section` and
 `project-device.update`, `project-device.insert`, `project-device.delete` and
-`project-device.sync-rows`, all with schema version `1`. Other command types
+`project-device.sync-rows` as well as `project.update-settings`, all with
+schema version `1`. Other command types
 are rejected. Insert commands contain the complete entity or circuit block
 with stable ids; delete commands include the expected parent identity. Circuit
 snapshots contain zero, one or multiple complete device rows. Move commands
@@ -136,6 +137,18 @@ These write endpoints execute the typed `project-device.update`,
 returns `409 PROJECT_REVISION_CONFLICT`. Updating a project device still never
 synchronizes linked circuit rows implicitly.
 
+### Project Settings
+
+- `PUT /projects/:projectId`
+  - request:
+    `{ "expectedRevision": 12, "singlePhaseVoltageV": 230, "threePhaseVoltageV": 400 }`
+  - executes `project.update-settings` as one atomic revision
+  - response:
+    `{ "project": { ... }, "revision": { ... }, "history": { ... } }`
+  - persistent Undo/Redo restores both voltage values together
+  - unchanged values are rejected without creating a revision; a stale
+    revision returns `409 PROJECT_REVISION_CONFLICT`
+
 Example:
 
 ```json

docs/current-architecture.md

@@ -175,6 +175,12 @@ unverknüpft und vollständig unverändert sind. Gerät, Linkänderungen, Revisi
 und Historienstapel teilen dieselbe Transaktion. Create, Import aus der globalen
 Gerätebibliothek und Delete laufen über dieselbe Command-Grenze; ihre Antworten
 liefern Gerät und aktualisierten Historienstand an die Projektseite zurück.
+`project.update-settings` versioniert die beiden Projekt-Standardspannungen als
+eine atomare Änderung. Der Store leitet das inverse Kommando aus dem
+gespeicherten Projekt ab und schreibt Werte, Revision und Historienstapel
+gemeinsam. `PUT /api/projects/:projectId` verlangt deshalb
+`expectedRevision`, liefert Projekt plus aktualisierten Historienstand und
+besitzt keinen separaten direkten Settings-Schreibweg mehr.
 
 ## Projektgeräte
 

docs/project-history-and-external-model-architecture.md

@@ -252,6 +252,9 @@ Completed foundation:
 - `project-device.insert` and `project-device.delete` preserve stable device
   ids; delete undo restores links only from complete unchanged disconnected-row
   snapshots in the same transaction
+- `project.update-settings` persists both project voltage defaults, its exact
+  inverse, revision and history transition atomically; the project page and
+  existing PUT route require the current expected revision
 
 Remaining constraints before completing project version history:
 

docs/spec/07-implementation-phases-todo.md

@@ -438,6 +438,9 @@ Implemented foundation:
 - ProjectDevice synchronization and disconnect endpoints also require
   `expectedRevision`; their UI undo uses project-wide persistent history and
   the obsolete direct restore/reconnect write paths are removed
+- project voltage settings use `project.update-settings`; both values, inverse,
+  revision and history transition commit atomically and the former direct
+  settings write is removed
 - revision metadata, change-set payloads and the project counter are committed
   in one SQLite transaction
 - a stale expected revision produces no history writes