Agent config not persisted when switching between agent settings

[isCopyman]

Bug Description

When configuring different agents in the settings panel, switching from one agent's config to another causes the first agent's settings to revert to defaults.

Steps to reproduce:

1. Open Mysti settings panel
2. Configure Claude Code — set model to Opus 4.6
3. Switch to configure Codex
4. Switch back to Claude Code — model has reverted to 4.5 (default)

Expected behavior: Each agent's configuration should be saved independently and persist when switching between agent settings.

Actual behavior: Navigating away from an agent's config panel resets its settings to defaults.