perf(debug-trace-server): build the witness execution form once per block

[flyq]

Summary

Every trace request deep-cloned the block's LightWitness out of the shared Arc<BlockData> (data.witness.clone() — the multi-hundred-KB-to-MB kvs/levels maps) and then rebuilt the LightWitnessExecutor direct-lookup table from scratch, two O(witness) passes paid on every debug_traceTransaction (transaction responses are never response-cached) and on every block-level response-cache miss or bypass (JS, mux, struct-logger-with-flags). Surfaced by the review pass on #184 as the largest remaining hot-path allocation; pre-existing, so fixed here separately.

Change

BlockData.witness now stores the LightWitnessExecutor — witness plus lookup table — built once where the BlockData is assembled (DB load, remote fetch, test fixtures) and shared by every request served from that entry, including repeated traces of a hot block. The trace entry points (trace_block, trace_transaction, parity_trace_block, parity_trace_transaction) and TracingEnv borrow it (&LightWitnessExecutor); no per-request clone or table rebuild remains. LightWitnessExecutor gains light_witness() (for extract_code_hashes and witness-size accounting) and lookup_table_memory_bytes(), which the block-data cache weigher now charges alongside the witness payload so the cache budget reflects the stored table.

Testing

cargo test --workspace: 374 passed / 0 failed; clippy / fmt / cargo-sort clean.

Notes

Based on #184 (liquan/chore/upgrade-reth-2.3) — merge after it lands.

[mega-maxwell]

Claude review status

Living comment — rewritten in place. The review workflow keeps this single comment up to date instead of posting a new one each round, so it always describes the latest reviewed commit and the earlier text is intentionally gone. No reply is needed here; reply to a finding in its own review thread, and answer an open question in a reply on this PR. The next review round reconciles your answer.

🛠️ Review did not finish

Attempted head 889c39f3 · updated 2026-08-11T01:22:31+00:00

This round did not publish: MODEL_ACTION_FAILED in phase review_retry. Anything listed below is from the last round that did. Re-run the workflow or push a new commit to try again.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.9%. Comparing base (99485a5) to head (889c39f).

Files with missing lines	Patch %	Lines
crates/stateless-core/src/light_witness.rs	0.0%	7 Missing ⚠️

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