feat: enhance JsonCodeEditor with autoFocus support

[chenyme]

Summary

Improve the chat model parameter configuration dialog so the JSON editor can reliably receive focus and accept input. JsonCodeEditor now supports autoFocus, avoids emitting change events during controlled value synchronization, preserves focus when external values are applied, and disables Monaco editContext to avoid browser input compatibility issues.

The model configuration dialog now keeps the JSON editor mounted across mobile tab switches and enables autofocus when opening the dialog, preventing the editor from losing its input state or focus when switching between JSON and visual configuration.

Change type

• Bug fix
• Feature
• Documentation
• Refactor
• Configuration / deployment
• Security hardening
• Other

Affected areas

• Frontend / UI
• Backend / API
• Authentication / authorization
• Conversations / streaming
• Files / RAG / extraction
• Model routing / providers
• MCP / tools
• Billing / payments
• Admin console
• Deployment / Docker / configuration
• Documentation

Verification

• Not run; reason: not available from the provided commit evidence.

Screenshots, API examples, or logs

N/A

Configuration, migration, and compatibility notes

No backend API, database schema, deployment, or configuration changes.

Documentation

• Documentation is not needed for this change.
• Documentation was updated.
• Documentation still needs to be updated.

Security and privacy

• No secrets, tokens, credentials, local config, or personal data are included.
• User data access remains scoped by authenticated user context unless an admin-only path explicitly requires broader access.
• Security-sensitive behavior was reviewed, including authentication, authorization, provider routing, file processing, billing, and admin APIs where relevant.

Checklist

• I searched existing issues and pull requests.
• Changes are focused and do not include unrelated refactors.
• Tests or static verification were run where practical.
• User-facing behavior, deployment steps, API contracts, or configuration changes are documented.
• Generated artifacts are included only when this project explicitly requires them.
• Caches, build output, .pyc files, .env files, and local storage data are not committed.