Fix errors such as "org.jetbrains.dokka.model.DClass ScrollState cannot be merged with org.jetbrains.dokka.model.DObject ScrollState" in dokkaGeneratePublicationHtml (#115)

* Initial plan

* Fix Dokka DClass/DObject merge error for ScrollState and LazyItemScope

Change `actual object ScrollState` to `actual class ScrollState` in jsMain
to fix Dokka's inability to merge DClass and DObject models. Apply the
same fix to `LazyItemScope` which had the same expect class/actual object
mismatch. Reuse a single LazyItemScope instance since it's stateless.

Co-authored-by: ShreckYe <27768951+ShreckYe@users.noreply.github.com>
Agent-Logs-Url: https://github.com/huanshankeji/compose-multiplatform-html-unified/sessions/fb46b1bd-1f94-4165-b19a-6bc80235c64b

* Add some comments and simplify

* Complete PR: update workflow to deploy Dokka API docs to GitHub Pages alongside demo

- Update demo-gh-pages.yml to run dokkaGeneratePublicationHtml alongside
  sideBySideBrowserDistribution and copy the Dokka HTML output to the
  site under an `api/` subdirectory
- Update workflow name to reflect it deploys both demo and API docs
- Fix copilot-setup-steps.yml to use ubuntu-latest (matching main)

Co-authored-by: ShreckYe <27768951+ShreckYe@users.noreply.github.com>
Agent-Logs-Url: https://github.com/huanshankeji/compose-multiplatform-html-unified/sessions/fe6d1cc2-55ae-4670-a884-abf1758ec816

* Revert "Complete PR: update workflow to deploy Dokka API docs to GitHub Pages alongside demo"

This reverts commit dba83da.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: ShreckYe <27768951+ShreckYe@users.noreply.github.com>
Co-authored-by: Yongshun Ye <ShreckYe@gmail.com>

Author: Copilot

common/src/jsMain/kotlin/com/huanshankeji/compose/foundation/Scroll.js.kt

@@ -28,10 +28,12 @@ val imitateComposeUiLayoutHorizontalScrollPlatformModifier =
 
 @Composable
 actual fun rememberScrollState(initial: Int): ScrollState =
-    ScrollState
+    ScrollState()
 
+
+// used to be `actual object`, but but Dokka fails with it
 @Stable
-actual object ScrollState
+actual class ScrollState
 
 actual fun Modifier.verticalScroll(state: ScrollState): Modifier =
     platformModify { verticalScroll() }

common/src/jsMain/kotlin/com/huanshankeji/compose/foundation/lazy/LazyDsl.js.kt

@@ -29,7 +29,7 @@ actual class LazyListScope {
         contentType: Any?,
         content: @Composable LazyItemScope.() -> Unit,
     ) =
-        addComposable { LazyItemScope.content() }
+        addComposable { LazyItemScope().content() }
 
     actual fun items(
         count: Int,
@@ -39,7 +39,7 @@ actual class LazyListScope {
     ) =
         addComposable {
             repeat(count) { index ->
-                LazyItemScope.itemContent(index)
+                LazyItemScope().itemContent(index)
             }
         }
 }

common/src/jsMain/kotlin/com/huanshankeji/compose/foundation/lazy/LazyItemScope.js.kt

@@ -12,7 +12,8 @@ import com.huanshankeji.compose.ui.Modifier
 @LazyScopeMarker
 @JvmDefaultWithCompatibility
 */
-actual object LazyItemScope {
+// used to be `actual object`, with which Dokka fails
+actual class LazyItemScope {
     // I am not sure whether these implementations work perfectly.
 
     actual fun Modifier.fillParentMaxSize(