Frontend: fix Agent Chat JSON rendering for model outputs

[igaurab]

Summary

This PR fixes cases where valid/near-valid model JSON responses were rendered as markdown text in Agent Chat instead of structured JSON.

What changed

• Updated /Users/igaurab/i/akd-debugger/frontend/src/components/agents/agent-chat-view.tsx parsing logic to:
  • Try full-message JSON parsing first (before markdown/code-fence segmentation).
  • Extract balanced JSON objects/arrays from mixed-content messages.
  • Normalize common model-output quirks before parsing:
    • smart quotes
    • BOM
    • hidden unicode whitespace/control characters
    • trailing commas before } / ]

Why

Some model responses contain small formatting artifacts even when they are conceptually JSON, causing strict parse failure and fallback to markdown rendering.