fix: the keyboard shortcuts the player has always advertised

The transport buttons have said "Play (space)" and "Full screen (f)"
since they were built, with nothing listening for either key. Pressing
f did nothing, which is exactly what a broken fullscreen button looks
like.

Both now work, verified in the running app: f enters and leaves
fullscreen, space plays and pauses. Space is prevented from also
pressing whichever button has focus, and neither fires while typing in
a field or alongside a modifier.

Escape now asks to leave fullscreen before the player considers
closing, so one keypress cannot drop you all the way back to the feed.

The button itself was never broken: it was checked on a downloaded
video, on a stream, and inside a window already in macOS fullscreen,
entering and leaving each time.

src/components/Player.tsx

@@ -299,8 +299,9 @@ export default function Player({
   // Escape backs out, as it does everywhere else in the app.
   useEffect(() => {
     const onKey = (e: KeyboardEvent) => {
-      // In fullscreen the browser already handles Escape; closing the player
+      // In fullscreen, Escape is the transport bar's to handle: it leaves
-      // as well would drop you all the way back to the feed.
+      // fullscreen. Closing the player as well would drop you all the way back
+      // to the feed in one keypress.
       if (e.key === "Escape" && !document.fullscreenElement) leave();
       // Arrow keys only when the video does not own them for seeking.
       if (e.key === "ArrowLeft" && e.shiftKey) onPrev?.();

src/components/PlayerControls.tsx

@@ -253,6 +253,38 @@ export default function PlayerControls({
     }
   }, [stageRef, onActivity]);
 
+  /**
+   * The shortcuts the buttons advertise. Their tooltips have promised
+   * "(space)" and "(f)" all along with nothing listening, and Escape left
+   * fullscreen nowhere: WebKit does not handle it for an element made
+   * fullscreen this way, so pressing it did nothing and the only way out was
+   * to find the button again.
+   */
+  useEffect(() => {
+    const onKey = (e: KeyboardEvent) => {
+      // Never while typing, and never over a shortcut of the system's own.
+      const t = e.target as HTMLElement | null;
+      if (t && (t.tagName === "INPUT" || t.tagName === "TEXTAREA" || t.isContentEditable)) return;
+      if (e.metaKey || e.ctrlKey || e.altKey) return;
+
+      if (e.key === " " || e.code === "Space") {
+        // Or the space would also press whichever button has focus.
+        e.preventDefault();
+        const v = videoRef.current;
+        if (!v) return;
+        if (v.paused) void v.play().catch(() => {});
+        else v.pause();
+        onActivity?.();
+      } else if (e.key === "f" || e.key === "F") {
+        void toggleFull();
+      } else if (e.key === "Escape" && document.fullscreenElement) {
+        void document.exitFullscreen();
+      }
+    };
+    window.addEventListener("keydown", onKey);
+    return () => window.removeEventListener("keydown", onKey);
+  }, [videoRef, toggleFull, onActivity]);
+
   const pct = duration > 0 ? (time / duration) * 100 : 0;
 
   return (