Check if reusing the encoder is worth it

A lot of effort has been spent reusing decoders. But encoders are always created from scratch. Check if reusing encoders is worth it, or if the benefit is marginal.

The issue names no files, tests, or entry points. Locate the existing decoder-reuse work and the encoder construction path, then measure whether reusing encoders provides a meaningful benefit over creating them from scratch. Done means a documented, evidence-based decision about whether encoder reuse is worthwhile.

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