[Tekgodfrey]

Title

fix(notifications): restore exact prior state on undo and fix Shift+R shortcut

Description

Closes #1225

This PR ensures that NotificationCenter's undo actions restore the exact prior state the user had, makes undo actions resilient against category mute preferences, and fixes the Shift+R keyboard shortcut so it fires reliably in real browsers while ignoring inputs in editable fields.

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Undo Semantics & Architecture

1. Exact Undo for "Mark All as Read"

• Prior State Capture: handleMarkAllAsRead filters and captures only the IDs of notifications that were unread at execution time (notifications.filter(n => !n.read).map(n => n.id)).
• Restoration: Triggering "Undo" calls undoRead(unreadIds), marking only those captured items as unread. Notifications that were already read before the action maintain their read state.
• Idempotency: Clicking Undo multiple times is protected with an execution guard, and calling undoRead with the same IDs is an idempotent state transition.

2. Merge-Safe Undo for "Clear All"

• Snapshot & Window: When "Clear all" is clicked, a snapshot of the current notifications is captured before clearing the list, and an undo toast is displayed for 6 seconds.
• Pure Merge: Calling restoreNotifications(snapshot) merges the cleared snapshot with any notifications that arrived or updated during the undo window via the pure helper mergeNotifications(snapshot, current, cap).
• Deduplication & Sorting: Notifications are deduplicated by id (with newer arrivals taking precedence), sorted descending by timestamp (newest first), and capped at the 100-notification limit.
• Idempotency: Clicking Undo twice does not duplicate notifications.

3. Category Preferences Bypass (bypassPreferences)

• New Option: Added optional bypassPreferences?: boolean to AddToastOptions.
• Behavior: When bypassPreferences: true is set, addToast bypasses category mute checks (such as preferences.system = false).
• Policy: Reserved exclusively for undo toasts and critical alerts to prevent user actions from silencing the only mechanism to revert destructive changes.

4. Keyboard Shortcut (Shift+R)

• Key Matching: Changed e.key === 'r' to e.key.toLowerCase() === 'r' alongside e.shiftKey to account for standard browser keyboard event dispatching where holding Shift sets e.key === 'R'.
• Editable Element Guard: Added isEditableTarget(e.target) to suppress the shortcut if focus or the event target is inside an <input>, <textarea>, <select>, or isContentEditable element.
• Scope: Preserved the requirement that the shortcut only activates when the panel is open (isPanelOpen === true) and unreadCount > 0.

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Regression Proof

• Row 1 (2 unread & 3 read, Mark all, Undo): Failed on main because undoRead(prior.map(n => n.id)) marked all 5 notifications unread.
• Row 4 (preferences.system = false, Mark all): Failed on main because the undo toast defaulted to category 'system' and addToast returned '', suppressing the toast.
• Row 5 (Shift+R with panel open): Failed on main because the existing test "activates mark all read with Shift+R keyboard shortcut" dispatched R with Shift, which failed to match e.key === 'r'.

All 3 scenarios now pass reliably.

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Verification Results

Test Suite

npm test -- --run src/components/notifications/NotificationCenter.test.tsx src/context/__tests__/notificationMerge.test.ts

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[Tekgodfrey]

@greatest0fallt1me kindly review sir