[andrebrait]

Follow-up to #230.

Problem

1. Read and unread entries in the Notifications tab looked almost the same: unread rows had a 7px dot beside the time and a faint tint, and read rows used the same text styling.
2. Every toast landed in the Notifications tab, including "Saved", copy results, update notices and agent notify calls, so the notifications the user needs to act on were buried.

Changes

• Read state: unread rows show an accent dot in a leading slot and a bold --text title on the tinted row. Read rows have a --text-muted regular-weight title and no tint. The description keeps --text-muted: in several themes --text-dim has higher contrast than --text-muted, so it would not dim the text.
• Only pushable types are listed: toast.* records into toastHistory only with the new history: true option. useNotifications sets it for session notifications (completed, input, error, model switch, the NOTIFICATION_TYPES that can also be pushed), including the toast fallback when a system notification cannot be shown. The notify host tool no longer records into the history.
• A reused id is unread again: record used to keep the read state of a reused id so that update notices re-shown on every tab focus did not badge again. Update notices are no longer listed. Session notifications reuse <sessionId>:<type> as their id, so keeping the read state made a session's next notification of the same type arrive already read.

Overlap: #240 and #242 touch toastHistory.record. With this PR, #242's keepRead option is no longer needed, because the update notices are not recorded. Whichever PR lands second needs a small rebase.

Verification

• toast.test.mjs: plain toasts stay out of the history, history: true toasts are listed, and a reused id is unread again.
• toast.click.test.mjs: a delivered session notification is listed with its <sessionId>:<type> id and is unread. The test fails if history: true is removed from useNotifications.
• NotificationList.test.mjs: only the unread row carries the unread marker.
• npm test 1347 tests, 0 failures. Typecheck and eslint are clean.
• Dev server: two notifications were marked read by leaving the tab, then a third arrived. The new notification showed the dot and a bold title, the read ones were dimmed, and an "OMP update available" toast did not appear in the list.