feat(canvas): delete a canvas with a confirm and an undo window

[adamleithp]

What

Adds Delete… to a canvas's … menu (it had none), and puts both delete paths behind a confirm dialog + an undo window.

Screen.Recording.2026-07-28.at.19.41.59.mov

• Canvas header … menu and the canvases-grid card menu now open a quill AlertDialog ("Delete canvas") instead of deleting on click — the grid one used to delete immediately, no confirmation.
• Confirming does not delete yet. The canvas is marked pending and the host isn't told until the "Deleted artifact" toast's timer (8s, matching the archive-undo window) expires. Undo just cancels the timer, so nothing is ever recreated.
• Pending canvases stay in their lists rather than vanishing: the artifacts row swaps its template icon for a pulsing trash can, turns its accent red, reads "Deleting…", and stops opening. The grid card dims behind the same icon. Undo restores them in place — no re-insert, no reorder.
• Deleting from inside a canvas navigates to the space's artifacts list. The commit therefore runs outside React (module-level timer + hostClient) so it survives that unmount.
• If the delete fails, the pending mark clears (the canvas comes back) and an error toast explains why.

delete is only tracked when it actually commits; a cancelled one tracks the new delete_undo action type.

Files

• deleteCanvasWithUndo.ts — the undo window: mark pending → schedule commit → toast with Undo. Re-deleting the same canvas restarts the window instead of stacking commits.
• stores/pendingCanvasDeleteStore.ts — state-only zustand map of ids inside their window.
• WebsiteLayout.tsx, WebsiteDashboardsIndex.tsx, WebsiteChannelArtifacts.tsx — menus, dialogs, deleting state.
• useDashboards.ts — exposes invalidateDashboards for the out-of-React commit.

Testing

4 unit tests in deleteCanvasWithUndo.test.ts (defers the send, undo cancels outright, failure restores + toasts, re-delete restarts). Full @posthog/ui suite passes (2303).

Manually:

1. Artifacts → canvas … → Delete… → confirm → row stays with a pulsing red trash icon and "Deleting…", click does nothing → Undo → back to normal in place.
2. Same, let the toast expire → row gone once the list refreshes; reload confirms it's really deleted.
3. Delete from inside a canvas → lands on Artifacts with that row already pulsing.
4. Canvases grid → delete → card dims with the trash overlay → Undo restores it.
5. Offline → confirm → after 8s the canvas reappears with "Couldn't delete canvas".

🤖 Generated with Claude Code

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[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit fc5334e.}