Add B² Network mainnet support

[a10zn8]

Summary

• Bump emerald-grpc and foundation/src/main/resources/public submodules to add-bsquared tips.
• B² Network mainnet (chain-id 223 / 0xdf, grpcId 1158) — OP Stack Bitcoin L2, native token BTC.

Verification

• ./gradlew clean chainscodegen regenerates Chain.kt with BSQUARED__MAINNET(1_158, "BSQUARED_MAINNET", "Bsquared Mainnet", "0xdf", BigInteger("223"), …).
• Local smoke test against https://mainnet.b2-rpc.com: upstream reaches status=[OK/1], height ~32.5M, archive=true, client geth v1.101315.2.

Companion PRs

• emerald-grpc: Add CHAIN_BSQUARED__MAINNET constant emerald-grpc#155
• public: Add B² Network mainnet public#218
• dproxy: https://github.com/drpcorg/dproxy/pull/2547
• dshackle: Add B² Network mainnet support #826
• nodecore: Add B² Network mainnet support nodecore#180
• infra: https://github.com/drpcorg/infra/pull/4644

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