fix(proxy): send ask_followup_question questions as array, not string

[Hughhhhcoder]

Problem

Fixes #1101.

CodeBuddy's ask_followup_question tool schema requires the questions parameter to be an array. However MemoryProxy/src/session/codebuddy/form.ts's buildFollowupQuestionArgs() wraps the question list with JSON.stringify(), producing:

{"title":"...","questions":"[{\"id\":\"team\",...}]"}

Newer CodeBuddy clients reject this tool call with:

Error calling tool: Tool call arguments for ask_followup_question were invalid:
invalid argument type for questions, expected array, received string

As a result the session-init form never renders, the user cannot pick an agent/task, retries exhaust (asset-confirm max retries, abandoning), and the whole conversation bypasses the memory pipeline.

Root cause

The only CodeBuddy form builder stringifies questions, while every other client form builder (claude-code, codex, dsh, workbuddy) already emits questions as a real array (e.g. return { questions } / JSON.stringify({ questions })).

Fix

• Return the questions array directly from buildFollowupQuestionArgs().
• Introduce a FollowupQuestion interface and type the downstream response builders (OpenAI/Anthropic, streaming and non-streaming) with questions: FollowupQuestion[] instead of questions: string.

Verification

• tsc --noEmit — no new type errors in src/session/codebuddy/ (remaining errors are pre-existing and unrelated).
• Runtime check via buildFormResponse() for OpenAI non-streaming / OpenAI streaming / Anthropic non-streaming: questions is now serialized as a JSON array in all three paths.

{"title":"...","questions":[{"id":"team","question":"...","options":["OTA-Platform (h45wed8k)"],"multiSelect":false}]}

[Maxwell-Code07]

Thank you so much for your attention and contribution! We will arrange an internal review for this PR shortly, and all feedback will be shared right here in the discussion.

[Hughhhhcoder]

Thanks for the quick update and for queueing the internal review — much appreciated. I’ll keep an eye on this thread and am happy to make any follow-up changes promptly once feedback comes in.