add Sei + Mode + Ronin + Immutable zkEVM to RPC bench cluster (benches 108-111)

[Flotapponnier]

Vague 1 chain expansion. 4 EVM chains re-audited live 2026-07-26, each with ≥4 clean no-key providers meeting the RPC cluster threshold.

Chains added

Chain	ChainID	Providers	Notes
Sei EVM	1329	sei-official, drpc, thirdweb, stakeme	July 3 audit had excluded (2 providers only); dRPC no longer caches + thirdweb + stakeme came online, restoring 4 clean
Mode	34443	mode-official, drpc, 1rpc, thirdweb	July 3 audit had excluded (3 providers); thirdweb added → 4 clean
Ronin	2020	ronin-official, drpc, tenderly, thirdweb	4 clean at launch
Immutable zkEVM	13371	immutable-official, drpc, tenderly, thirdweb	4 clean at launch

Files touched

• harnesses/rpc-capabilities/cmd/script/config.go — 4 chain entries with per-provider env-var overrides
• harnesses/chain-kpis/cmd/script/registry.go — DefiLlama slugs verified live (Mobula left empty pending key)
• src/lib/chains.ts — registry entries for /chains hub
• benchmarks/{sei,mode,ronin,immutable}-rpc.yml — 4 new bench specs

Verified

• All 4 chains: eth_chainId + eth_blockNumber respond 200 for all listed providers
• DefiLlama /v2/chains returns each name (Sei, Mode, Ronin, Immutable zkEVM)
• Spec validation: pnpm validate → 98 specs ✓