feat: add session undo and redo

2026-09-30 01:33:29 +02:00
parent d38584396b
commit 804f32c5fb
9 changed files with 411 additions and 14 deletions
@@ -101,6 +101,21 @@ uses on a first run, so "reset" and "a brand-new browser" cannot drift apart.
 Both are preceded in the UI by a JSON backup download that must succeed before
 the destructive write is attempted.

+## Session undo and redo
+
+The snapshot store keeps up to 50 prior saved datasets in memory. A changed
+`mutate` adds one step after its write succeeds; an unchanged mutation adds
+none. Undo and redo run through the same queue and persist their target dataset
+before changing the visible snapshot or either history stack. A failed write
+therefore leaves both the data and the available undo/redo actions intact.
+
+Import and reset clear the stacks only after their write succeeds. They are
+whole-dataset replacement flows with backup-first protection, not ordinary
+undoable edits. History is not in `Dataset` or IndexedDB and vanishes on reload.
+The header reads a stable history capability snapshot from the store to enable
+its controls; keyboard shortcuts skip editable fields so browser text undo
+still works.
+
 ## Money

 A float, deliberately, with two rules that make it safe: