fix: Protocol ready-for-query after error, and tests for protocol messages

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Built bundles:

• Postgres WASM: https://github.com/electric-sql/pglite/actions/runs/10830395752/artifacts/1924551151
• Interim build files: https://github.com/electric-sql/pglite/actions/runs/10830395752/artifacts/1924551235
• PGlite: https://github.com/electric-sql/pglite/actions/runs/10830395752/artifacts/1924574254
• Demos: https://github.com/electric-sql/pglite/actions/runs/10830395752/artifacts/1924587138

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