fix: notification settings UX improvements and in-app banner fixes

[Just-Insane]

Summary

Overhaul notification settings UX and fix several notification bugs.

Bug fixes

• Push notifications always silent — resolveSilent in the service worker now always returns false, leaving sound/vibration decisions entirely to the OS and Sygnal push gateway. The in-app sound setting no longer affects push behaviour.
• In-app banner not appearing on desktop — The banner was erroneously gated behind a mobileOrTablet() check. It now fires on all platforms when In-App Notifications is enabled.
• In-app banner placement — Rendered as position: fixed in ClientLayout (single render point, full viewport width, z-index: 9999). Doesn't displace any page content.
• In-app banner shows "sent an encrypted message" — Events reaching the banner are already decrypted by the SDK. isEncryptedRoom: false is now passed so the actual message body is always shown when message content preview is enabled.
• Desktop OS notifications not firing when page is hidden — The OS notification block now runs before the visibilityState !== 'visible' guard, which only gates the in-app banner and audio. Notifications now fire even when the browser window is minimised.
• iOS lock screen media player — After HTMLAudioElement.play(), mediaSession.playbackState is cleared after a short delay, dismissing the lock screen widget. If in-app media (e.g. a video in a room) has since registered its own metadata the media session is left untouched.

Settings page improvements

• Move badge display settings (Show Message Counts, Direct Messages Only, Always Count Mentions) from Appearance → Notifications.
• Rename "Mobile In-App Notifications" → "In-App Notifications"; show the toggle on all platforms.
• Rename "Notification Sound" → "In-App Notification Sound" to clarify it only controls in-page audio, not push sound.
• Fix "System Notifications" description (removed incorrect claim that mobile uses the in-app banner).
• Add notification levels info button (ⓘ) to All Messages, Special Messages, and Keyword Messages headings explaining Disable / Notify Silent / Notify Loud.
• Add descriptive text under each notification section heading.
• Collapse the two @room push rules into a single "Mention @room" control: routes to IsRoomMention (m.mentions, MSC3952) on modern servers, or AtRoomNotification on older servers. Synapse mirrors both rules so showing them separately caused an apparent sync loop where setting one immediately reset the other.
• Add "Follows your global notification rules" subtitle to the "Default" option in the per-room notification switcher.
• Default "In-App Notifications" to off for all platforms — users can opt in per-device in Notifications settings.
• Default "Show Message Counts" (badge numbers) to off — badges show a number only for direct mentions by default (Discord-style).

Changed files

File	Change
src/app/pages/client/ClientNonUIFeatures.tsx	iOS media session clear; OS notifications before visibility guard; isEncryptedRoom: false for banner; remove mobileOrTablet() gate
src/app/pages/client/ClientLayout.tsx	Single <NotificationBanner> render point
src/app/components/notification-banner/NotificationBanner.css.ts	position: fixed; top: 0; left: 0; right: 0
src/app/features/settings/notifications/SystemNotification.tsx	In-App toggle on all platforms; rename labels; add Badges section
src/app/features/settings/notifications/AllMessages.tsx	Descriptive text + levels hint
src/app/features/settings/notifications/SpecialMessages.tsx	Descriptive text + levels hint; collapse @room to single control
src/app/features/settings/notifications/KeywordMessages.tsx	Descriptive text + levels hint
src/app/features/settings/notifications/NotificationLevelsHint.tsx	New component — ⓘ popover
src/app/components/RoomNotificationSwitcher.tsx	"Follows your global rules" subtitle on Default
src/app/features/settings/cosmetics/Themes.tsx	Remove badge settings (moved to Notifications)
src/app/state/settings.ts	useInAppNotifications: false; showUnreadCounts: false defaults
src/sw/pushNotification.ts	resolveSilent = () => false — OS handles sound
src/sw.ts	Remove notificationSoundEnabled from SW postMessage payload

[7w1]

In-app notifs should probably be enabled by default on mobile. Also the changeset needs to be like 1 one, or multiple files detailing the individual updates. Tbh, this might be better split up into multiple PRs it's kind of a lot of changes all at once for things that very likely have edge cases.

[Just-Insane]

Sounds good, I was thinking it was quite large.

This PR has been split into four focused draft PRs, each with its own changeset:

PR	Scope
#252 — fix: notification delivery bugs	SW resolveSilent, OS notification timing, in-app banner platform gate, iOS media session, encrypted banner text
#253 — fix: in-app notification banner placement	Move NotificationBanner to ClientLayout as position: fixed, remove from Room.tsx
#254 — feat: notification settings page improvements	Label renames, badge settings move, @room rule collapse, levels hint, descriptive text, per-room switcher subtitle
#255 — fix: default badge unread counts to off	showUnreadCounts: true → false (Discord-style); useInAppNotifications left as mobileOrTablet() per your feedback

This PR (#239) can be closed once the individual ones are reviewed.

[Just-Insane]

Closed as superseded (split out into smaller PRs)