Potential experiments

fix(app): blur mature embed images and videos

fix(app): load small list avatars eagerly (#1918)

fix(app): hide decorative country and region flags from screen readers (#1917)

fix(app): replace the whole +: token when picking a reaction emoji (#1916)

fix(app): keep composer markdown highlighting aligned on long messages (#1915)

fix(app): honour the animation setting for composer custom emoji (#1914)

fix(app): keep the character counter inside the composer box (#1913)

fix(app): honour motion settings in composer autocomplete previews (#1912)

fix(app): reuse highlighted code instead of flashing plain text (#1911)

fix(app): let custom branding override the built-in meta description (#1910)

fix(app): show a still ban image under reduced motion or data saver (#1909)

fix(app): keep avatar stack entries keyed by user across re-renders (#1908)

fix(app): keep avatar stack entries keyed by user across re-renders

fix(app): show cached auth splash art without a fade-in flash (#1907)

perf(app): keep gateway and layer manager off the auth session path (#1906)

fix(app): size auth entity icons to their reserved box (#1905)

fix(app): keep paging when the jumped-to message is missing (#1904)

fix(app): drive the message list window from one load state machine (#1903)

perf(app): window sticker picker rows by offset instead of observers (#1902)

fix(app): tell the user when a search query has nothing to search (#1901)