fix: keep a chat pane mounted while its composer reads attachments

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

frontend/src/lib/components/copilot/chat/AIChatInput.svelte

@@ -378,7 +378,14 @@
 	)
 	$effect(() => {
 		chatHost.setComposerStaged(composerKey, editingMessageIndex, stagedBytes)
-		chatHost.setComposerHasDraft(composerKey, !draft.isEmpty || pendingFileBytes > 0)
+		chatHost.setComposerHasDraft(
+			composerKey,
+			!draft.isEmpty ||
+				pendingFileBytes > 0 ||
+				pendingImages > 0 ||
+				pendingBlobs > 0 ||
+				ingestionHolds > 0
+		)
 	})
 	$effect(() => () => chatHost.clearComposerStaged(composerKey))
 

frontend/src/lib/components/copilot/chat/AIChatManager.svelte.ts

@@ -2838,11 +2838,7 @@ export class AIChatManager implements ChatViewHost {
 	 *  queued message (whose text may be empty when it carries only attachments
 	 *  or context). */
 	get hasUnsentInput(): boolean {
-		return (
-			this.#composersWithDraft.size > 0 ||
-			!this.#queuedDraft.isEmpty ||
-			this.queuedContext !== undefined
-		)
+		return this.#composersWithDraft.size > 0 || this.#hasQueuedMessage()
 	}
 
 	/** Release the outgoing-files reservation identified by `key` (a per-send token).