test(playground): fix TipTap regression test build on mr-template-editor

[Rishabh060105]

Closes N/A

Restores the Netlify/build pipeline on mr-template-editor after the new TipTap regression test introduced a TypeScript build failure.

This PR addresses a follow-up issue from PR #878 where src/tests/components/TiptapTemplateEditor.test.tsx stored a plain object in modelManager. That worked in the mocked Vitest path, but failed tsc because the Zustand store expects a real ModelManager instance. As a result, npm run build failed and the Netlify deploy checks could not complete successfully.

Changes

• Updated src/tests/components/TiptapTemplateEditor.test.tsx to use a real ModelManager instance instead of a plain { id: string } object.
• Kept the fix scoped to the regression test only, without changing TiptapTemplateEditor, store behavior, or any user-facing runtime flow.
• Re-ran local verification with:
  • npm run build
  • npx vitest run src/tests/components/TiptapTemplateEditor.test.tsx
  • npx vitest run src/tests/store/setData.test.tsx
  • npm run test:unit

Flags

• This PR intentionally keeps the fix scoped to the present mr-template-editor build regression rather than broadening into runtime/editor changes from PR feat(templateMark): add rich text editor #878.
• Backup-branch differences in vite.config.ts and the rebuild/model-loading path were reviewed, but no broader rollback was needed once the TypeScript test failure was fixed.
• No screenshots or video are included because this is a build/test fix rather than a visual UI change.

Screenshots or Video

N/A - this is a build/test fix. The behavior is covered by build and unit test verification rather than a visual UI change.

Related Issues

• Pull Request feat(templateMark): add rich text editor #878

Author Checklist

• Ensure you provide a DCO sign-off for your commits using the --signoff option of git commit.
• Vital features and changes captured in unit and/or integration tests
• Commits messages follow AP format
• Extend the documentation, if necessary
• Merging to mr-template-editor from fork:branchname

[Rishabh060105]

Hi @mttrbrts I opened this follow-up to restore the Netlify/build checks on mr-template-editor.

Changes in this PR:

• Updated src/tests/components/TiptapTemplateEditor.test.tsx so the regression test uses a real ModelManager instance instead of a plain object.
• Kept the fix scoped to the test only; there are no runtime changes to the editor or store.
• Re-validated locally with:
  • npm run build
  • npx vitest run src/tests/components/TiptapTemplateEditor.test.tsx
  • npx vitest run src/tests/store/setData.test.tsx
  • npm run test:unit

What I found on the base branch:

• The Netlify failures were caused by the production build path failing in src/tests/components/TiptapTemplateEditor.test.tsx.
• The test stored a plain object in modelManager, but tsc expects a real ModelManager, so npm run build failed before deploy could complete.

So this PR is intended as a narrow build-fix follow-up on top of mr-template-editor.