feat(defaults): giga executor enabled by default, matching seid

[bdchatham]

Why

baseDefaults() never sets GigaExecutor, so the Go zero value renders [giga_executor] enabled = false / occ_enabled = false into every app.toml sei-config produces — for every mode, on every render. seid's own default is the opposite (DefaultConfig = {Enabled: true, OCCEnabled: true}, giga/executor/config/config.go), and seid only applies its code default when the key is absent — so the fleet has been pinned to the v2 executor by an accident of zero values, not a decision. (Found while verifying why the EIP-7623 receipt-parity specs pass against every nightly node: no platform-managed node executes EVM txs through the giga path at all. Adversarial review confirmed the render chain: legacyGigaExecutor has no omitempty, so the section is always present-with-false, and neither seid launch args nor env carry any giga_executor override on live harbor nodes.)

What

Set GigaExecutor{Enabled: true, OccEnabled: true} in baseDefaults(), matching seid. Explicit-false overrides still render (which is why this is a value change, not the omit-when-unset pattern used for write_mode/evm-ss-split — omitempty on a bool would silently drop an operator's explicit false).

⚠️ Blast radius — review before merging

• Every node without an explicit giga_executor.enabled override flips to the giga executor on its next config render + seid restart. Only two prod files pin the key today (arctic-1/archive-0-1a, pacific-1/shadow-giga); everything else rides the default. If prod should stay v2, land explicit false pins before this merges, or gate this by mode.
• Older pinned binaries (e.g. the nightly upgrade-from image) will read enabled = true into whatever giga maturity they shipped — TestNightlyChainUpgrade exercises exactly this.
• Enabling giga also flips tmtypes.SkipLastResultsHashValidation — consensus-adjacent; deserves deliberate sei-chain sign-off.
• Downstream: nightly release-test suites then run against giga-executor nodes — the desired end-state for guarding sei-chain#3768, but only once #3768 merges; sequencing matters or the parity specs go red.

Testing

go build ./... + go test ./... green. No existing test pinned the old false default (registry/intent tests assert key presence, not value).

🤖 Generated with Claude Code

[cursor]

PR Summary

High Risk
Flips the default execution path for most fleet nodes on the next config render and seid restart, with consensus-adjacent behavior when giga is enabled; only a few prod configs currently pin false.

Overview
baseDefaults() now sets GigaExecutor to enabled=true and occ_enabled=true, aligned with seid’s DefaultConfig.

Previously, leaving GigaExecutor unset meant Go zero values were always written into generated app.toml, so every sei-config render effectively forced the v2 executor off and overrode seid’s in-binary default when the key was absent. Operators who need v2 must set giga_executor.enabled=false explicitly on the next render/restart.

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