feat: 4K downloads, watch progress, player controls, new icon

Window chrome: titleBarStyle Overlay (Transparent left the native bar in
place, white in dark mode, with a dead strip beneath it). The app now
paints that strip itself, so it matches the page background.

Player: prev/next through the feed, a full-screen button, a spinner
while a stream resolves, Open on YouTube on downloaded videos too, and
the description collapsed behind a disclosure.

Downloads default to Best, which reaches real 4K — above 1080p YouTube
serves VP9/AV1, verified to play natively in WKWebView here. Audio stays
pinned to AAC because Opus in MP4 would be silent. A Compatible setting
keeps the old 1080p H.264 behaviour. Files are now named
'<ISO date> - <title> [<id>].mp4'.

Watch progress is recorded and drawn under thumbnails like YouTube's,
and reopening a video resumes where it left off.

Tiles clamp every text line to a fixed height so they share a baseline,
and the search field no longer clips its placeholder.

Fixes a Picture-in-Picture leak: WebKit kept a detached video playing
after the player closed, so a second video could play over the first
with no way to stop it. Every exit path now tears the element down.

src/api.ts

@@ -9,6 +9,7 @@ import type {
   FeedItem,
   ImportPreview,
   Prereqs,
+  Quality,
   RefreshProgress,
   RefreshSummary,
 } from "./types";
@@ -22,8 +23,11 @@ export const listFeed = (filter: FeedFilter) =>
 
 export const refreshFeeds = () => invoke<RefreshSummary>("refresh_feeds");
 
-export const downloadVideo = (videoId: string) =>
-  invoke<void>("download_video", { videoId });
+export const downloadVideo = (videoId: string, quality: Quality) =>
+  invoke<void>("download_video", { videoId, quality });
+
+export const savePlayback = (videoId: string, position: number, duration: number) =>
+  invoke<void>("save_playback", { videoId, position, duration });
 
 export const cancelDownload = (videoId: string) =>
   invoke<void>("cancel_download", { videoId });