Build Browser Flow Studio in Playground With Live Compile Preview

[dgenio]

Description

Current playground runs demos, but flow authoring is still code-first.

Use case

Evaluators should design and validate a flow without local setup.

Proposed solution

• Add visual flow editor in playground.
• Show live compile result, warnings, and schema mismatch hints.
• Preview execution trace using sample input.
• Export and import .flow.yaml from the editor.
• Add mobile-safe layout and keyboard navigation.

Alternatives considered

• Keep playground read-only.
• Build desktop-only editor.
• Depend on external diagram tools.