New scoped useReducer hook covering the full single-snapshot lifecycle —
LOAD_FOR_DATE / SET_LINE_VALUE / SAVE / DELETE / PREFILL_FROM_PREVIOUS /
RESET — with the following semantics:
- 'new' mode (?date= absent or no snapshot at that date) creates the row
at save time only, so abandoning the form does not leave an empty
snapshot behind;
- 'edit' mode loads existing lines + prefills the values map;
- prefillFromPrevious copies simple-kind values from the most recent
earlier snapshot (priced branch is a no-op + TODO Issue #140);
- save() flips 'new' -> 'edit' on success and updates the URL ?date=
so refresh keeps the user in edit mode;
- snapshotDate is immutable in edit mode (UI guard, matches spec).
New SnapshotEditPage at /balance/snapshot:
- date picker (native input type=date — matches the AdjustmentForm /
TransactionFilterBar / PeriodSelector pattern, no new dep)
- per-category groups of accounts with one value field each
- prefill button (disabled when no earlier snapshot exists, with
tooltip explaining why)
- delete button with double-confirmation modal that requires retyping
the snapshot date before the destructive action enables.
New SnapshotEditor (groups by category sort_order) and SnapshotLineRow
(simple variant — single value field per account) components.
Route /balance/snapshot wired in App.tsx.
Refs #146
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
