feat: add a dedicated generative UI editing flow

[wgqqqqq]

Summary

• add a dedicated generative UI editing flow from the tool card into the right-side widget source panel
• sync widget source edits back into the tool card and persisted session state, and add widget export/static rendering support
• restore right-click context highlighting for selected generative UI elements in the tool card
• remove the ACP quick start and implementation summary docs

Testing

• pnpm --dir src/web-ui run type-check