[Website] Add error notices and delete confirmation modal to site management

[bgrgicak]

Motivation for the change, related issues

Follow-up to PR feedback on #3401. The PlaygroundSitesAPI methods throw descriptive errors for MCP consumers, but UI components were silently swallowing them. Additionally, site deletion used window.confirm, which is inconsistent with the rest of the modal-based UI and blocks the main thread.

Implementation details

Error notices in modals

• Rename modal: catches errors from sitesAPI.rename() and displays them in a <Notice> component.
• Save modal: surfaces the actual error message (instead of a generic string) and moves the error notice above the action buttons for visibility.
• Delete modal (new): catches errors from sitesAPI.delete() and displays them inline.

Delete confirmation modal

• Replaces window.confirm with a new DeleteSiteModal component, consistent with the existing rename/save modal pattern.
• Adds DELETE_SITE modal slug and siteSlugToDelete UI state to the Redux store.
• Both the site info panel and saved playgrounds overlay now dispatch the modal instead of calling window.confirm.

API documentation

• Adds JSDoc comments with @param, @returns, and @throws tags to every method on the PlaygroundSitesAPI interface.

Minor cleanups

• Inlines getActiveSiteOrThrow — each call site now checks and throws with a context-specific message ("No active site selected").
• persistTemporarySite now lets showDirectoryPicker errors propagate instead of silently returning, so callers can handle cancellation.
• Removes post-persist storage === 'none' safety-net checks that are no longer needed.

Testing Instructions

Testing Instructions

1. In save-site-modal/index.tsx, add throw new Error('test') before the persistTemporarySite call in handleSubmit
2. Open the Playground website and try saving a temporary site — confirm the error appears as a notice inside the modal
3. Repeat for rename-site-modal/index.tsx (before sitesAPI.rename()) and delete-site-modal/index.tsx (before sitesAPI.delete())
4. Remove the temporary throw statements
5. Save, rename, and delete a site — confirm each operation succeeds and the modal closes

[Copilot]

Pull request overview

This PR improves site-management UX by surfacing API errors inside modals and replacing blocking window.confirm deletion with a dedicated modal flow.

Changes:

• Add inline error notices to rename/save/delete site modals so API errors aren’t silently swallowed.
• Replace window.confirm with a new DeleteSiteModal and Redux UI state to track which site is being deleted.
• Add JSDoc (@param, @returns, @throws) documentation across the PlaygroundSitesAPI interface.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/playground/website/src/lib/state/redux/slice-ui.ts	Adds DELETE_SITE modal slug and siteSlugToDelete UI state/action to support delete modal flow.
packages/playground/website/src/lib/state/redux/site-management-api-middleware.ts	Adds API JSDoc and updates error/guard behavior for active-site operations and deletion messaging.
packages/playground/website/src/lib/state/redux/persist-temporary-site.ts	Lets directory picker errors propagate so callers can show cancellation/errors in UI.
packages/playground/website/src/components/site-manager/site-info-panel/index.tsx	Switches delete action from window.confirm + API call to opening the delete modal with selected slug.
packages/playground/website/src/components/saved-playgrounds-overlay/index.tsx	Switches delete action to open delete modal (instead of confirming + calling API directly).
packages/playground/website/src/components/save-site-modal/index.tsx	Displays real error messages via <Notice> and moves error notice above action buttons.
packages/playground/website/src/components/rename-site-modal/index.tsx	Shows rename errors inline via <Notice> and unifies form layout via shared modal form CSS.
packages/playground/website/src/components/modal/style.module.css	Adds shared .modal-form styling for consistent modal form layout.
packages/playground/website/src/components/layout/index.tsx	Wires DELETE_SITE slug to render the new DeleteSiteModal.
packages/playground/website/src/components/delete-site-modal/index.tsx	Introduces a delete confirmation modal with inline error handling.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.