feat(ext): handcraft the whole ext from scratch

AI coding doesn't work for MV3 extensions.
Threading was an unfixable mess.
Removed everything and rebuilt by hand.

packages/extension/src/agent/RemotePageController.background.ts

@@ -0,0 +1,40 @@
+/**
+ * background logics for RemotePageController
+ * - redirect messages from RemotePageController(Agent, extension pages) to ContentScript
+ */
+
+// chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
+// 	if (message.type !== 'PAGE_CONTROL') {
+// 		return
+// 	}
+
+export function handlePageControlMessage(
+	message: { type: 'PAGE_CONTROL'; action: string; payload: any; targetTabId: number },
+	sender: chrome.runtime.MessageSender,
+	sendResponse: (response: unknown) => void
+): boolean {
+	const { action, payload, targetTabId } = message
+
+	if (action === 'get_my_tab_id') {
+		sendResponse({ tabId: sender.tab?.id || null })
+		return false
+	}
+
+	chrome.tabs
+		.sendMessage(targetTabId, {
+			type: 'PAGE_CONTROL',
+			action,
+			payload,
+		})
+		.then((result) => {
+			sendResponse(result)
+		})
+		.catch((error) => {
+			sendResponse({
+				success: false,
+				error: error instanceof Error ? error.message : String(error),
+			})
+		})
+
+	return true // async response
+}