QuickTime/hevc embed playback does not fallback to software decoding

Reproduction steps

Send a video attachment in hevc format.
Attempt to play video on a computer that does not support hardware hevc decoding, such as my Quadro 2000.
On web, video does not play. On desktop, only the sound plays.

Expected behaviour

The video player should use software decoding of hevc content when the graphics driver does not support hardware decoding.

Actual behaviour

On desktop, the video is a black rectangle, and only the audio plays. On the web client, the sound does not play either.

Build information

Canary Desktop 2026.1103.194246, Web 2026.1104.25856, Windows 11 10.0.26300 (x64), Electron 44.10.0, Chrome 152.0.7977.169, Node 24.22.1, Locale en-US

Platform

Windows