Hand playback to a native shell (#45)

CarPlay and Android Auto cannot render a web view. Both are template
surfaces, and the only audio they will control is the host's own AVPlayer
or ExoPlayer -- so an app that is "the web UI plus CarPlay" is really "the
web UI whose audio engine is native", and the page had no way to give
playback away.

web/src/native.ts replaces the playback surface of the page's media element
with one that forwards to the host and synthesises the events back. Nothing
in player.ts changes: it only ever speaks to the element, so the player bar,
the row buttons, the EQ bars and the keyboard shortcuts keep working as they
did. Video stays in the page, since CarPlay is audio-only and a native video
layer under a web view buys nothing. In a browser none of it installs.

Position and read are the host's to write. player.ts has been bitten before
by a stale position -- one left paused in another tab saved its older place
over where you had got to -- and a backgrounded web view is exactly that
tab: frozen, holding a time from minutes ago, while the host plays on. So
the beacon becomes a request for the host to save its own clock.

tests/native-bridge.js is what holds the two ends together, and it earned
its place immediately: the src setter called removeAttribute('src'), which
the shim's own override turned into a stop() that switched it back off one
line after enabling it. Silent, and only visible in a car. The stub DOM
moved to tests/dom-stub.js so that test and page-smoke share one harness
rather than two copies.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -11,6 +11,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - A Glass theme, light and dark, with frosted see-through panels after Apple's Liquid Glass. It
   goes solid when the system asks for less transparency or more contrast.
+- The page can hand playback to a native app. Opened inside an iOS or Android shell, an episode
+  plays through the host's own player instead of the page's, so it keeps going when the screen
+  locks and the car can control it; the player bar, the row buttons and the keyboard shortcuts
+  work as they always did. Video still plays in the page. In a browser nothing changes.
 
 ## [0.8.3] - 2026-09-19