feat: notify other users when a version is restored

[leotrs]

Summary

• Added useRestoreNotification composable that watches Y.js awareness states for other users' restoring field
• When another connected user starts a version restore (null → versionId transition), shows an info toast: "{name} restored a previous version — Your editor has been updated"
• Wired into Canvas.vue where the shared awareness ref is provided
• Filters out self (no toast for own restores), handles missing user info gracefully, auto-cleans up on unmount

Test plan

• 6 unit tests for useRestoreNotification (all pass)
• Existing 28 Canvas.vue tests still pass
• Existing 12 useVersionRestore tests still pass
• Manual: open same file in two browser tabs, restore a version in one — other tab should show toast

🤖 Generated with Claude Code

[netlify]

✅ Deploy Preview for rsm-studio-frontend canceled.

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🔨 Latest commit	9837445
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[netlify]

✅ Deploy Preview for rsm-studio-site canceled.

Name	Link
🔨 Latest commit	9837445
🔍 Latest deploy log	https://app.netlify.com/projects/rsm-studio-site/deploys/69d282353d1be6000845f7de

[leotrs]

Needs human review

What changed: Added a toast notification that appears when another connected user restores a previous version of a document ("Alice restored a previous version — Your editor has been updated").

Review checklist:

1. Open the deploy preview: https://deploy-preview-369--rsm-studio-frontend.netlify.app
2. Log in with two different accounts (or two browser tabs with different sessions)
3. Open the same document in both tabs
4. In one tab, restore a previous version
5. Verify the other tab shows an info toast: "{name} restored a previous version" with description "Your editor has been updated"
6. Verify the tab that performed the restore does NOT show a toast to itself
7. Verify the toast auto-dismisses after ~5 seconds

What to look for:

• Toast appears promptly after the restore action
• Toast does not appear for the user who initiated the restore (self-filtering)
• No duplicate toasts if the restore action is repeated
• Toast text is correct and readable (no "undefined" or "Someone" when user info is available)
• No console errors in the browser during the flow
• Edge case: disconnect one tab's network briefly, reconnect, and restore — verify no spurious toasts

[github-actions]

Preview Deploy

Frontend: https://pr-369--rsm-studio-frontend.netlify.app
Backend: https://aris-backend-staging.fly.dev (staging)
API docs: https://aris-backend-staging.fly.dev/docs

Test user: preview-pr-369@aris.pub

This preview will be destroyed when the PR is closed.

[leotrs]

Needs human review

What changed: When another connected user restores a previous version, a toast notification now appears: "{name} restored a previous version — Your editor has been updated."

Review checklist:

1. Open a document in two separate browser tabs (logged in as different users, or same user in two tabs)
2. In Tab A, open the version history and restore a previous version
3. In Tab B, verify an info toast appears with the restoring user's name and the message "Your editor has been updated"
4. Verify the toast auto-dismisses after ~5 seconds
5. Verify that Tab A (the user who performed the restore) does NOT see a toast for their own action
6. Test with a user who has no display name — toast should show "Someone restored a previous version"

What to look for:

• Toast appears promptly after the restore action (not delayed or duplicated)
• Toast styling matches existing info toasts in the app
• No duplicate toasts if the same user restores multiple times in quick succession
• No toast appears on initial page load when another user already has a restoring state
• Editor content actually updates to match the restored version (existing behavior, but verify it still works)

[leotrs]

Needs human review

What changed: New toast notification appears to collaborators when another user restores a previous version of a document.

Review checklist:

1. Open the same file in two separate browser tabs (logged in as different users, or two windows with distinct sessions)
2. In Tab A, open the version history and restore a previous version
3. In Tab B, verify an info toast appears: "{name} restored a previous version — Your editor has been updated"
4. Verify Tab A does NOT show the toast to itself
5. Verify the toast auto-dismisses after ~5 seconds
6. Test with a user that has no display name — toast should say "Someone restored a previous version"

What to look for:

• Toast appears promptly after the restore action (no noticeable delay)
• Toast text is correct and includes the restoring user's name
• No duplicate toasts (restoring the same version twice should show two toasts, but clearing the restoring state should not trigger one)
• No toast on initial page load when another user already has a restoring state set
• No console errors related to awareness state changes

🤖 Generated with Claude Code