ci: add gas report workflow with baseline comparison

[jonaprieto]

Move gas reporting into a dedicated gas-report.yml workflow, keeping the contracts CI lean. The new workflow provides gas snapshot, per-function gas report, contract sizes (with EVM 24KB limit warnings), and a baseline diff vs. main on every PR. The baseline is cached on each main merge and PRs automatically compare against it, surfacing regressions with delta and percentage inline in a sticky PR comment.

[jonaprieto]

CI is green and artifacts are live. Here's the first run producing them:

https://github.com/anoma/pa-evm/actions/runs/24377241026

The gas-report artifact contains both a .gas-snapshot (per-test gas costs) and a gas-report.txt (per-function breakdown for all Benchmark contracts). Artifacts are retained for 30 days and labeled with the branch and commit SHA for easy comparison across PRs.

[github-actions]

Gas Report

Total benchmark gas: 202,096,997 — no baseline yet, diff available after first merge to main

Gas Snapshot — per-test gas consumption

Test	Gas
Benchmark:test_aggregated_proof_gas_cost_is_fixed	32,870,549
Benchmark:test_empty_transaction_gas_cost_is_fixed	33,460
Benchmark:test_execute_00	20,116
Benchmark:test_execute_01_01_agg	694,584
Benchmark:test_execute_01_01_reg	1,185,130
Benchmark:test_execute_02_02_agg	1,662,585
Benchmark:test_execute_02_02_reg	4,361,352
Benchmark:test_execute_05_01_agg	1,991,226
Benchmark:test_execute_05_01_reg	5,424,650
Benchmark:test_execute_10_01_agg	3,636,485
Benchmark:test_execute_10_01_reg	10,709,124
Benchmark:test_execute_15_01_agg	5,343,708
Benchmark:test_execute_15_01_reg	15,974,733
Benchmark:test_execute_20_01_agg	7,217,976
Benchmark:test_execute_20_01_reg	21,276,208
Benchmark:test_print_calldata_agg	8,257,151
Benchmark:test_print_calldata_reg	11,436,231
Benchmark:test_regular_proof_gas_cost_is_bound	70,001,729

Gas Report — per-function statistics

╭--------------------------------------------------+-----------------+---------+---------+----------+---------╮
| src/ProtocolAdapter.sol:ProtocolAdapter Contract |                 |         |         |          |         |
+=============================================================================================================+
| Deployment Cost                                  | Deployment Size |         |         |          |         |
|--------------------------------------------------+-----------------+---------+---------+----------+---------|
| 10327775                                         | 21324           |         |         |          |         |
|--------------------------------------------------+-----------------+---------+---------+----------+---------|
|                                                  |                 |         |         |          |         |
|--------------------------------------------------+-----------------+---------+---------+----------+---------|
| Function Name                                    | Min             | Avg     | Median  | Max      | # Calls |
|--------------------------------------------------+-----------------+---------+---------+----------+---------|
| execute                                          | 29815           | 4873847 | 3483778 | 17879605 | 13      |
|--------------------------------------------------+-----------------+---------+---------+----------+---------|
| simulateExecute                                  | 29878           | 3347417 | 2110267 | 17879673 | 26      |
╰--------------------------------------------------+-----------------+---------+---------+----------+---------╯

Contract Sizes — EVM bytecode size (24,576 B limit)

Contract	Runtime (B)	Initcode (B)	Margin (B)
BlockTimeForwarder	531	557	24,045
CommitmentTree	521	1,068	24,055
ControlID	213	241	24,363
Groth16Verifier	1,728	1,754	22,848
NullifierSet	347	373	24,229
ProtocolAdapter	20,137	21,228	4,439
RiscZeroGroth16Verifier	5,300	8,607	19,276
RiscZeroVerifierEmergencyStop	2,364	2,642	22,212
RiscZeroVerifierRouter	2,778	2,996	21,798
SHA256	119	147	24,457
VersioningLibExternal	123	147	24,453

---

_{Generated by CI — commit 8398d0e — 2026-04-15 20:06 UTC}

[heueristik]

This is very cool! Can we add it into a separate workflow so that the complexity and runtime of the contracts test workflow is not increased?