Add KDoc to the features/messages API interfaces

Document HtmlConverterProvider, MessageComposerContext,
PinnedEventsTimelineProvider, the MessagesEntryPoint node proxy and the voice
message composer factory.

HtmlConverterProvider carries the ordering constraint that matters: the converter
is rebuilt from the Compose theme, so Update has to be composed before provide is
called.

MessagesEntryPoint and its Callback are navigation plumbing and out of scope.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

features/messages/api/src/main/kotlin/io/element/android/features/messages/api/MessageComposerContext.kt

@@ -17,5 +17,6 @@ import io.element.android.libraries.textcomposer.model.MessageComposerMode
  * the composer is in a thread, if it's editing a message, etc.
  */
 interface MessageComposerContext {
+    /** What the composer is currently doing: writing a new message, editing one, replying, or composing in a thread. */
     val composerMode: MessageComposerMode
 }

features/messages/api/src/main/kotlin/io/element/android/features/messages/api/MessagesEntryPoint.kt

@@ -50,7 +50,16 @@ interface MessagesEntryPoint : FeatureEntryPoint {
         callback: Callback,
     ): Node
 
+    /**
+     * Lets callers outside this feature drive an already created messages node, for navigation that has to happen after it is attached.
+     */
     interface NodeProxy {
+        /**
+         * Opens a thread on top of the messages screen, suspending until the thread node is attached.
+         *
+         * @param threadId the thread to open.
+         * @param focusedEventId the event to scroll to within the thread, or `null` to open at the latest message.
+         */
         suspend fun attachThread(threadId: ThreadId, focusedEventId: EventId?)
     }
 }

features/messages/api/src/main/kotlin/io/element/android/features/messages/api/pinned/PinnedEventsTimelineProvider.kt

@@ -10,4 +10,9 @@ package io.element.android.features.messages.api.pinned
 
 import io.element.android.libraries.matrix.api.timeline.TimelineProvider
 
+/**
+ * A [TimelineProvider] whose active timeline holds the pinned events of the room, rather than its live events.
+ *
+ * It exists as its own type so that it can be injected where only the pinned timeline is wanted.
+ */
 interface PinnedEventsTimelineProvider : TimelineProvider

features/messages/api/src/main/kotlin/io/element/android/features/messages/api/timeline/HtmlConverterProvider.kt

@@ -11,9 +11,16 @@ package io.element.android.features.messages.api.timeline
 import androidx.compose.runtime.Composable
 import io.element.android.wysiwyg.utils.HtmlConverter
 
+/**
+ * Provides the converter that turns message HTML into styled text.
+ *
+ * The converter depends on the current theme and typography, so [Update] must be composed before [provide] is called.
+ */
 interface HtmlConverterProvider {
+    /** Rebuilds the converter from the current Compose theme; call this once, high in the composition of a screen that renders messages. */
     @Composable
     fun Update()
 
+    /** Returns the converter built by the last [Update] call. */
     fun provide(): HtmlConverter
 }

features/messages/api/src/main/kotlin/io/element/android/features/messages/api/timeline/voicemessages/composer/VoiceMessageComposerPresenter.kt

@@ -12,7 +12,13 @@ import io.element.android.libraries.architecture.Presenter
 import io.element.android.libraries.matrix.api.timeline.Timeline
 
 fun interface VoiceMessageComposerPresenter : Presenter<VoiceMessageComposerState> {
+    /**
+     * Creates a presenter for one voice message composer.
+     */
     interface Factory {
+        /**
+         * @param timelineMode the timeline the recording will be sent to, which matters for threads in particular.
+         */
         fun create(timelineMode: Timeline.Mode): VoiceMessageComposerPresenter
     }
 }