ci: Optimise Nx workflow

[lachlancollins]

• Run nx-cloud start-ci-run immediately after checkout
• Use shared setup action from tanstack/config
• Reduce dynamic-changesets

[nx-cloud[bot]]

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✅ Successfully ran 1 target

- [`nx affected --targets=test:format,test:sherif,test:knip,test:lib,test:types,build --parallel=3`](https://cloud.nx.app/runs/KrHPyOvQJo?utm_source=pull-request&utm_medium=comment)

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