introduce a new serialization for the generator in UnfinishedBlock

[arvidn]

just like FullBlock, where the generator is serialized as a byte blob. To parse an UnfinishedBlock, with the new format, we no longer need to deserialize CLVM.

This mirrors the changes in #1456 and #1345 .

---

Note

Medium Risk
Changes consensus-relevant block serialization and parsing for unfinished blocks on the network; backward compatibility for version 0 is preserved, but any mismatch with FullBlock or peers on v1 encoding would be high impact.

Overview
UnfinishedBlock now mirrors FullBlock’s dual generator wire format: version 0 keeps CLVM Program plus transactions_generator_ref_list; version 1 stores length-prefixed raw bytes in transactions_generator_buffer and omits the ref list, so peers can parse the block without deserializing CLVM. A custom Streamable implementation packs version and presence into the transactions_generator Option prefix byte (bit 0 = present, bit 1 = v1).

FullBlock parsing now derives version with prefix >> 1 instead of a single-bit check, and adds tests that prefix bytes with bits 2–7 set are rejected as InvalidFullBlock. UnfinishedBlock gets the same strict prefix rules via InvalidUnfinishedBlock (new error in chia-traits). Python stubs expose transactions_generator_buffer and version on UnfinishedBlock.

Comment-only renames from “Optional” to “Option” appear in a few protocol files.

^{Reviewed by Cursor Bugbot for commit 2798fa8. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coveralls-official]

Coverage Report for CI Build 28535161482

Coverage increased (+0.1%) to 81.664%

Details

• Coverage increased (+0.1%) from the base build.
• Patch coverage: 27 uncovered changes across 1 file (253 of 280 lines covered, 90.36%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
crates/chia-protocol/src/unfinished_block.rs	258	231	89.53%
Total (2 files)	280	253	90.36%

Coverage Regressions

No coverage regressions found.

---

Coverage Stats

Relevant Lines:	19192
Covered Lines:	15673
Line Coverage:	81.66%
Coverage Strength:	11771006.39 hits per line

---

💛 - Coveralls

[arvidn]

@cursor review

[cursor]

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit d07310a. Configure here.}