Shadow the feed list on a phone only while it is open (#151)

On a phone the feed list is a drawer slid off the screen to the left, and it kept its shadow
there, which fell back across the page: the left 30px or so of the top bar and everything under
it were darker, in every theme (Glass light 231,233,243 at the edge against 246,247,255). Beside
the flat strip iOS paints above the page it made a seam at the top-left corner (#147).

Hiding the closed drawer instead (visibility) would also have done it, but every phone test
starts by waiting for the feed list to be visible, which off the screen it still counts as.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- On a phone, the closed feed list no longer shades the left edge of the page with its shadow.
 - On an iPhone, the top bar's colour runs all the way up behind the status bar and the Dynamic Island, with no band of another colour above it.
 - A feed's buttons stay on one row on a narrow phone, and the reader's buttons stay together instead of breaking across lines under a long feed name.
 - A moment's DNS failure no longer marks a feed as failing for a day or calls it gone: iPX tries it again in ten minutes. One failed lookup one morning left 205 podcasts unread, uncategorised and labelled gone until the next day. A name that does not resolve is said to be maybe gone, and only once it has been failing a day, on its Directory page as on its own.