[Demo] Tanstack db demo update

[stevensJourney]

Fix TanStack DB Demo Module Resolution & Add E2E Tests

Problem

The TanStack DB demo fails to run with pnpm dev, showing the following error:

✘ [ERROR] Could not resolve "@powersync/common"

    ../../node_modules/@tanstack/powersync-db-collection/dist/esm/schema.js:1:27:
      1 │ import { ColumnType } from "@powersync/common";
        ╵                            ~~~~~~~~~~~~~~~~~~~

Root Cause

This is caused by pnpm's package hoisting behavior in the monorepo:

1. @tanstack/powersync-db-collection is hoisted to the root node_modules folder
2. It declares @powersync/common as a peer dependency
3. The demo had @powersync/common as a direct workspace:* dependency, which symlinked it to the demo's node_modules only
4. When Vite/esbuild bundles @tanstack/powersync-db-collection from the root, it cannot resolve @powersync/common because it's not present at the root level

Solution

Remove the direct @powersync/common dependency from the demo. The package is already available transitively through @powersync/web, which resolves the hoisting issue.

Additional Changes

Added end-to-end tests for the demo that run outside of the monorepo context. These tests:

• Verify the demo loads correctly in a Vitest browser mode session
• Perform basic mutations and validate that TanStack DB detects and renders the changes correctly

[changeset-bot]

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Latest commit: ef6fcb7

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[Chriztiaan]

Tested this on my side, happy with the changes.

[LucDeCaf]

Tested it, looks good to me.