[AI-BUILDER-11] (frontend): preserve chat history and refactor

[kevinkim-ogp]

TL;DR

• Updates chat interface to preserve chat history on refresh
• Refactor and removed unused helper

How to test?

• Chat history is preserved on refresh
• Chat interface still works as intended

[kevinkim-ogp]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• [AI-BUILDER-15] PLU-605: chat feedback #1352
• [AI-BUILDER-14] feat: adds AI suggestions for form inputs #1364
• [AI-BUILDER-13] (frontend): refactor form modal content #1311
• [AI-BUILDER-12] (frontend): chat readiness check for steps preview #1363
• [AI-BUILDER-11] (frontend): preserve chat history and refactor #1365 👈 (View in Graphite)
• [AI-BUILDER-10] (backend): add chat readiness check #1362
• [AI-BUILDER-9] PLU-604 (frontend): Preview steps and create Pipe #1310
• [AI-BUILDER-8] PLU-603 (frontend): Chat interface #1309
• [AI-BUILDER-7] PLU-584 (backend): add api for chat streaming #1307
• [AI-BUILDER-6] PLU-584 (backend): setup api route #1306
• [AI-BUILDER-5] (frontend): add ai related deps #1305
• [AI-BUILDER-4]: create pipe from generated steps #1304
• [AI-BUILDER-3] (frontend): preview generated steps #1361
• [AI-BUILDER-2] PLU-595 (frontend): enter prompt #1303
• [AI-BUILDER-1] PLU-583 (backend): mutation to generate AI steps #1302
• [AI-2] PLU-583 (feat): add deps for AI and tracing #1360 : 1 other dependent PR (#1312 )
• [AI-1] (chore): bump zod and typescript #1359
• trunk/ai

This stack of pull requests is managed by Graphite. Learn more about stacking.