Fix crash loop: WebView touched off main thread during extraction cancellation

Root-caused via emulator stress test (rapid swiping through many articles):
withTimeoutOrNull's cancellation, and LaunchedEffect disposal when a page is
swiped away, both invoke invokeOnCancellation on kotlinx.coroutines.DefaultExecutor
rather than the calling coroutine's Main dispatcher. The handler called
webView.stopLoading()/destroy() directly, crashing with "A WebView method was
called on thread ..." on essentially every session once enough thin-content
articles were swiped past mid-extraction -- the reported crash loop. Now hops
back to the main looper before touching the WebView, and guards against a
double destroy() race between the JS-callback and cancellation paths.

Also fixed a real (non-crashing) leak: the visible reader WebView in
ReaderScreen was never destroy()-ed when its page left the pager, via
AndroidView's onRelease.

Reproduced pre-fix in ~80 rapid swipes on an emulator; post-fix, 320+ swipes
with real 107-feed data ran clean with stable native heap.

1 files changed, 6 insertions, 1 deletions

diff --git a/app/src/main/java/org/terst/feedreader/ui/ReaderScreen.kt b/app/src/main/java/org/terst/feedreader/ui/ReaderScreen.kt
index 692c198..cef17c5 100644
--- a/app/src/main/java/org/terst/feedreader/ui/ReaderScreen.kt
+++ b/app/src/main/java/org/terst/feedreader/ui/ReaderScreen.kt
@@ -231,7 +231,12 @@ private fun ReaderContent(articleId: String, onBack: () -> Unit) {
                             loadDataWithBaseURL(baseUrl, wrapHtml(content), "text/html", "UTF-8", null)
                         }
                     },
-                    update = { webView -> webView.loadDataWithBaseURL(baseUrl, wrapHtml(content), "text/html", "UTF-8", null) }
+                    update = { webView -> webView.loadDataWithBaseURL(baseUrl, wrapHtml(content), "text/html", "UTF-8", null) },
+                    // AndroidView does not destroy() the underlying WebView on its own --
+                    // without this, swiping through many articles (each page holding its own
+                    // WebView) leaks a WebView's native resources per page and eventually
+                    // exhausts memory over a long reading session.
+                    onRelease = { webView -> webView.destroy() }
                 )
             } else if (isExtracting) {
                 CircularProgressIndicator(modifier = Modifier.align(Alignment.Center))