feat: playground landing page should direct users to MCP #69
Description
Summary
Navigating to /playground without a ?session= param currently auto-creates a new session and drops you into the editor. This is confusing because:
- Users don't understand the session model or how agents interact with the playground
- There's no indication that the playground is agent-first — designed for AI agents to drive via MCP
- Manual sessions created this way are disconnected from any MCP workflow
Current Behavior
/playground → instantly creates a session → shows editor with default shader
Proposed Behavior
/playground (no session param) → show an onboarding/landing view:
- Brief explanation: "The Shader Playground is designed for AI agents to write and iterate on shaders in real-time"
- How it works: "Connect your AI agent to ShaderBase's MCP server, then use
create_playgroundto start a session" - MCP connection details (endpoint URL, available tools)
- Maybe a "Try it manually" button that creates a session for users who want to experiment without MCP
/playground?session=<id> → current behavior (load session, show editor + canvas)
Why This Matters
The playground is agent-first by design (#52). The UX should reflect that — the primary entry point is through MCP, not through clicking a nav link. Humans opening /playground directly should understand the model and know how to connect their agent.
Design Notes
- Keep it simple — a single centered card with instructions, not a full page redesign
- Include a code snippet showing
create_playgroundtool usage - Link to MCP server docs/endpoint
- If we want to support manual experimentation, a secondary "Start manual session" button is fine