Add persistent history stacks

docs/circuit-list-editor-api.md

@@ -7,7 +7,14 @@ All paths below are mounted below `/api`. There is no Consumer application API.
 
 Project responses from `GET /projects` and `GET /projects/:projectId` include
 `currentRevision`. It currently exposes the persisted revision foundation only;
-no public history, undo or redo endpoint exists yet.
+no public undo or redo command exists yet.
+
+### Project History State
+
+- `GET /projects/:projectId/history`
+  - returns `currentRevision`, `undoDepth`, `redoDepth` and the current top
+    change-set id for both persistent stacks
+  - is read-only; the editor does not consume it yet
 
 ## Circuit-First Endpoints
 

docs/current-architecture.md

@@ -73,9 +73,12 @@ angeschlossen. Für Circuit- und Gerätezeilen-Feldänderungen existieren intern
 Command-Stores, die Fachänderung, automatisch erzeugtes inverses Kommando und
 Revision gemeinsam committen beziehungsweise zurückrollen können.
 Gerätezeilen-Kommandos bewahren dabei auch lokale ProjectDevice-Overrides und
-prüfen Projektzugehörigkeit von Verknüpfungen und Räumen. Die Stores sind noch
-nicht über die API oder das Grid aktiviert; serverseitiges Undo/Redo ist daher
-noch nicht verfügbar.
+prüfen Projektzugehörigkeit von Verknüpfungen und Räumen. Projektweite,
+persistente Undo-/Redo-Stacks verwalten die zulässige LIFO-Reihenfolge und
+verwerfen den Redo-Zweig bei einem neuen Benutzerkommando. Ihr Status ist über
+`GET /api/projects/:projectId/history` lesbar. Die schreibenden Command-Stores
+sind noch nicht über die API oder das Grid aktiviert; serverseitiges Undo/Redo
+ist daher noch nicht verfügbar.
 
 ## Projektgeräte
 

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

@@ -160,16 +160,24 @@ Completed foundation:
 - integration tests apply the generated inverse as a new `undo` revision and
   verify rollback for stale revisions and late history failures on both update
   command types
+- project-scoped relational undo/redo stacks persist eligible original change
+  sets independently from immutable audit revisions
+- stack transitions enforce LIFO order, keep undo/redo revisions out of the
+  eligibility stacks and clear the redo branch on a new user command
+- domain writes, audit revisions and stack transitions share one transaction;
+  a forced stack failure rolls all of them back
+- `GET /api/projects/:projectId/history` exposes current revision, stack depths
+  and top change-set ids without enabling mutation endpoints
 
-Remaining constraints before implementing history:
+Remaining constraints before completing persistent history:
 
 - extend the concrete project-scoped command union and executors beyond the
   internal Circuit and CircuitDeviceRow update slices; the generic versioned
   command envelope is complete
-- route domain writes and revision recording through one shared project
-  transaction boundary; the current revision repository only commits history
-  records and the counter together
-- expose revision state and history eligibility through the application API
+- route the remaining structural, synchronization and destructive domain
+  writes through the shared command, revision and stack transaction boundary
+- add public command execution plus undo/redo endpoints; read-only revision and
+  stack eligibility state is already exposed
 - replace the session-local frontend command stack only after server-side
   command execution and inverse application are complete
 - do not model IFCGUID as an overloaded circuit equipment identifier

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

@@ -361,7 +361,7 @@ Tasks:
 - route domain writes and history records through one shared transaction
 - define concrete serializable domain command descriptions and executors
   outside React
-- persist undo/redo eligibility on the server
+- [x] persist undo/redo eligibility on the server
 - add named and periodic logical project snapshots
 - restore a historical snapshot as a new revision
 - keep database backups separate from logical history
@@ -379,6 +379,12 @@ Implemented foundation:
 - an internal typed `circuit-device-row.update` command uses the same boundary,
   records derived ProjectDevice override metadata and rejects cross-project
   rows, device links and rooms
+- relational project-wide undo/redo stacks persist eligible original change
+  sets, enforce LIFO order and clear redo on a new user command
+- stack transitions are part of the domain/revision transaction and have
+  late-failure rollback coverage
+- a read-only project history endpoint exposes revision, stack depths and top
+  change-set ids
 - revision metadata, change-set payloads and the project counter are committed
   in one SQLite transaction
 - a stale expected revision produces no history writes