perf: suppress dead Cosmos events in giga executor path

[pdrobnjak]

Summary

• Adds GIGA_SUPPRESS_COSMOS_EVENTS=true env var flag to skip Cosmos-level event emission (coin_spent, coin_received, etc.) during giga executor tx execution
• Cosmos events in this path are constructed but never consumed: ExecTxResult.Events is never populated, events are not consensus-critical, and deterministicExecTxResult strips them
• EVM logs (Solidity events) flow through a separate path (tempState.logs → receipts) and are unaffected

Implementation

1. EventManager.suppressed field — EmitEvent/EmitEvents return immediately (no mutex, no append, no bech32 encoding)
2. NewSuppressedEventManager() constructor for the suppressed variant
3. DBImpl.cosmosEventsSuppressed — Snapshot() creates suppressed EventManagers
4. Finalize() skips flushEvents() loop entirely when suppressed

Profile impact (benchmark-compare.sh, 120s)

Mutex contention eliminated: -48.35s (7.6% of total)

• EventManager.EmitEvents: -48.21s
• sync.(*Mutex).Unlock: -48.35s

Allocations eliminated: ~1.65 GB

• Events.AppendEvents: -1,068 MB
• Events.AppendEvent: -729 MB

TPS was flat in isolation because the bottleneck shifts to Snapshot() → CacheMultiStore allocation. The contention and allocation savings will compound once that path is optimized.

Test plan

• giga/deps/xevm/state tests pass
• sei-cosmos/types tests pass
• Verify EVM logs still appear in receipts with flag enabled
• Run benchmark with GIGA_SUPPRESS_COSMOS_EVENTS=true

🤖 Generated with Claude Code

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Feb 17, 2026, 2:25 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.38%. Comparing base (fce7d6a) to head (2660165).

❗ There is a different number of reports uploaded between BASE (fce7d6a) and HEAD (2660165). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (fce7d6a)	HEAD (2660165)
sei-chain	1	0

Additional details and impacted files

@@                     Coverage Diff                     @@
##           pd/giga-block-cache-v2    #2904       +/-   ##
===========================================================
- Coverage                   57.22%   48.38%    -8.85%     
===========================================================
  Files                        2093      671     -1422     
  Lines                      171750    50621   -121129     
===========================================================
- Hits                        98285    24491    -73794     
+ Misses                      64687    23984    -40703     
+ Partials                     8778     2146     -6632     

Flag	Coverage Δ
sei-chain	?
sei-cosmos	48.19% <ø> (+<0.01%)	⬆️
sei-db	68.72% <ø> (ø)

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