Cursor prompt: Add WorkspaceRegistry

Prerequisites

Read:

• [ ] [ONTOUI.md](../WORKSPACE_RUNTIME.md`
• [ ] 0002-workspace-over-panel-model.md

Non-goals

• Migrate App.tsx routing
• Entity workspace rewrite

Current state

• App.tsx switch on PanelKind
• panels/ directory with one component per panel

Tasks

1. Create extension/webview-ui/src/workspaces/types.ts (WorkspaceDefinition, WorkspaceProps)
2. Create extension/webview-ui/src/workspaces/registry.ts with register/get/list
3. Register stub entries for entity, graph, query mapping to existing panel components
4. Add registry.test.ts

Acceptance criteria

• [ ] Registry returns registered workspace by id
• [ ] Existing panel components referenced not duplicated

Tests

• cd extension/webview-ui && npm test

Do not

• Do not remove ?panel= routing yet

References

• Cursor prompts index