Chaff/Habit glow-up in Nockchain

jam/cue serialization/deserialization for Nouns in nockvm/nockchain. I wrote an initial sketch "fast jam" that I will open source soon. Edward _significantly_ cleaned up the unholy-but-fast mess I made. That's where the chaff and habit crates came from. What remains is the "fast cue" counterpart to the "fast jam" and tightening up the testing and correctness.

Start by examining the chaff and habit crates in nockvm/nockchain and the existing “fast jam” serialization sketch. Determine the intended “fast cue” counterpart, then review the current testing and correctness coverage to define what remains; the issue does not name specific files or tests.

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