feat: implement ADK wrapper functions for Agent Engine sessions

[nohe427]

No description provided.

[gemini-code-assist]

Code Review

This pull request introduces a Firebase Cloud Functions wrapper proxy for Google Cloud's Agent Engine (ADK), providing secure, authenticated access to reasoning engine endpoints for client applications. The implementation includes session management, memory operations, and streaming query support. Key feedback includes correcting the Node.js runtime version in package.json, fixing a bug in adk.ts where streaming response data was incorrectly parsed as a string instead of a Protobuf value, and improving API error handling by replacing generic errors with structured HttpsError responses for unauthenticated requests.

[gemini-code-assist]

The Node.js version "24" is likely a typo or refers to a version not yet supported by Firebase Functions. It is recommended to use a stable LTS version like "22" or "20".

Suggested change

	"node": "24"
	"node": "22"

[gemini-code-assist]

The response.data field in the aiplatform SDK's stream response is a google.protobuf.Value object, not a Buffer. Using JSON.parse(response.data.toString('utf8')) will fail. Use helpers.fromValue(response.data) to correctly parse the Protobuf value into a JavaScript object. Additionally, using optional chaining ensures the code is resilient to unexpected response structures.

Suggested change

	const parsed = JSON.parse(response.data.toString('utf8'));
	chunks.push(parsed);
	if (parsed.content && parsed.content.parts) {
	fullText += parsed.content.parts.map((p: any) => p.text || "").join("");
	}
	const parsed = helpers.fromValue(response.data) as any;
	chunks.push(parsed);
	if (parsed?.content?.parts) {
	fullText += parsed.content.parts.map((p: any) => p.text || "").join("");
	}

[gemini-code-assist]

Import HttpsError to provide structured error responses to the client. This should be applied to all endpoint files.

Suggested change

	import { onCall } from "firebase-functions/v2/https";
	import { onCall, HttpsError } from "firebase-functions/v2/https";

[gemini-code-assist]

Use HttpsError with the unauthenticated code instead of a generic Error. Generic errors are returned to the client as INTERNAL (500), which hides the actual cause and is poor practice for API design. This pattern should be followed in all other endpoint files as well.

Suggested change

	if (!uid) {
	throw new Error("Unauthorized");
	}
	if (!uid) {
	throw new HttpsError("unauthenticated", "The function must be called while authenticated.");
	}