fix: mini player no longer overlaps a reader's own controls; chrome follows app theme, not the reading theme

[schmitzkr]

Two follow-up reports from on-device use:

"the mini player is over the book controls" when a book/reader screen is open

The floating mini player was only hidden on the dedicated Player screen
(onPlayer); every EPUB/comic/PDF reader has its own floating bottom bar
(page slider, chevrons) that the pill would sit on top of just the same.
Renamed the check to onReadingSurface and extended it to the EPUB and
page-format reader routes too — playback keeps running, the pill just
doesn't render over a screen that already has its own bottom controls,
same as it already didn't for Player.

"the reader shows pretty light themed controls when in dark mode ... the mini player stays dark, and i think it looks better when the controls match the main theme but the page can be different, sepia, white etc."

Reverses the previous session's chromeScheme change: the EPUB reader's
chrome (ReaderBar, the progress slider) now takes the app's own
light/dark setting again, same as the mini player and every other
screen, instead of following whichever reading theme is selected. The
reading theme still only changes the page background behind the
WebView. The two unrelated correctness fixes from that same change —
onColorFor()'s contrast-ratio fix and ReaderBar's explicit
contentColor — both stay; they were never about which theme the chrome
uses, only about it rendering legibly whichever one it's given.

Could not verify locally this round — two other builds already running
from another session on this box — pushing for CI to verify compilation.

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