Implement `core/gater`

[varex83]

Scope

Port charon/core/gater.go — the core-layer connection/peer gater. Distinct from the p2p-layer gater (crates/p2p/src/gater.rs), which is already implemented.

References

• Go: https://github.com/ObolNetwork/charon/blob/main/core/gater.go
• Tests: core/gater_test.go

Acceptance

• Public API matches the Go reference
• Tests ported and green
• cargo clippy --workspace --all-targets --all-features -- -D warnings clean

[emlautarom1-agent]

Port audit — core/gater (scope clarification)

• Status: 🔴 not started
• ⚠️ Scope clarification: in Charon this is core/gater.go — a ~45 non-test LOC DutyGater that decides whether a duty's slot/epoch is acceptable (rejects too-old / too-far-future duties). It is not the libp2p connection gater (p2p/gater.go, a separate concern already covered under the p2p layer). Please confirm the issue title means the DutyGater.
• Complexity: Simple
• Internal deps: app/eth2wrap✅
• Critical path: ✅ Yes (small but required) — DutyGater is passed into both the Consensus controller and ParSigEx at wiring time (app/app.go); the pipeline won't wire without it.

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Automated progress audit (2026-06-15). New comment only — no existing issue content was modified.