fix: handle nested response object in report agent chat

[back2zion]

Summary

• The /api/report/chat endpoint returns a nested response: {data: {response: {response: "text", sources: [], tool_calls: []}}}
• The frontend (Step5Interaction.vue) expected res.data.response to be a string, but it's an object
• This caused the chat UI to spin indefinitely as the object couldn't be rendered as message content

Fix

Added type check to extract the inner string when res.data.response is an object:

// Before
content: res.data.response || res.data.answer || 'No response',

// After
content: (typeof res.data.response === 'object' ? res.data.response.response : res.data.response) || res.data.answer || 'No response',

Test plan

• Verified /api/report/chat returns nested {response: {response: "..."}} structure
• Confirmed chat messages now render correctly after the fix