feat: integrate Blast (81457) as second-class Relay chain

[NeOMakinG]

Description

Integrate Blast (EVM chain ID 81457, CAIP eip155:81457) as a second-class citizen chain in ShapeShift Web, following the exact same pattern as Hemi.

This is PR 10 of 17 in a sequential chain integration series. These PRs must be reviewed and merged in order, as each builds on the previous one (stacked branches).

PR merge order:

1. Mantle (feat: integrate Mantle (chainId 5000) as second-class EVM chain #11905)
2. Cronos (feat: integrate Cronos (chainId 25) as second-class EVM chain #11910)
3. Sonic (feat: integrate Sonic (eip155:146) as second-class EVM chain #11923)
4. Unichain (feat: integrate Unichain (eip155:130) as second-class citizen via Relay #11924)
5. BOB (feat: integrate BOB (eip155:60808) as second-class citizen #11925)
6. Mode (feat: integrate Mode (eip155:34443) as second-class citizen #11926)
7. Soneium (feat: integrate Soneium (chainId: 1868) via Relay #11930)
8. Hemi (feat: integrate Hemi (chainId: 43111) via Relay #11931)
9. World Chain (feat: integrate World Chain (480) as second-class Relay chain #11932)
10. Blast (feat: integrate Blast (81457) as second-class Relay chain #11933) ← this PR
11. zkSync Era (feat: integrate zkSync Era (324) as second-class Relay chain #11934)
12. Story (feat: integrate Story (1514) as second-class Relay chain #11936)
13. Plume (feat: integrate Plume (98866) as second-class Relay chain #11937)
14. Flow EVM (feat: integrate Flow EVM (747) as second-class Relay chain #11938)
15. Celo (feat: integrate Celo (42220) as second-class Relay chain #11939)
16. Ethereal (feat: integrate Ethereal (5064014) as second-class Relay chain #11940)

Note: Linea (#11922) is already in develop.

What's included:

• CAIP constants and KnownChainIds enum entry (BlastMainnet = 'eip155:81457')
• HDWallet support flags across all wallet implementations (native, gridplus, ledger, metamask-multichain, trezor, walletconnectv2 = true; coinbase, keepkey, phantom, vultisig = false)
• BlastChainAdapter extending EvmBaseAdapter
• CoinGecko adapter with platform blast and native asset ID ethereum (ETH-native chain)
• Swapper integration: Relay and Across support
• Plugin, feature flag (Blast), CSP headers, viem/ethers clients, Zerion mapping
• All utility mappings (chainIdToFeeAssetId, getChainShortName, getNativeFeeAssetReference, etc.)
• ETH-native related asset index entry
• Asset generation script for Blast

62 files changed, 362 insertions, 3 deletions.

Issue (if applicable)

N/A

Risk

Low — This is a standard second-class chain integration behind a feature flag (Blast). No existing chain behavior is modified. All changes follow the established pattern used by Hemi and other EVM chains.

No existing protocols, transaction types, wallets, or contract interactions are affected. Blast support is additive and gated behind a feature flag.

Testing

Engineering

1. Enable the Blast feature flag via /flags route (click settings modal header 5 times)
2. Verify Blast appears in the chain selector
3. Verify Blast assets load from CoinGecko
4. Verify Relay and Across swapper routes include Blast
5. Run yarn lint and yarn type-check — both should pass

Operations

• 🏁 My feature is behind a flag and doesn't require operations testing (yet)

Screenshots (if applicable)

N/A — No visual changes; chain integration is behind a feature flag.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feat/integrate-blast-relay

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[gomesalexandre]

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