fix(zerox): exact Permit2 allowance and EIP-712 bind checks

[SashaMIT]

Description

execute_swap_on_0x previously:

1. Approved Permit2 with maxUint256 whenever the price response reported an allowance issue
2. Blind-signed quote.permit2.eip712 with no local binding checks

That combination means a compromised or MITM’d 0x response path can inherit an unlimited allowance and obtain signatures over attacker-controlled typed data.

This change:

• Approves only the swap’s sellAmount (not unlimited)
• Validates Permit2 EIP-712 verifyingContract, chainId, token, and amount against local swap intent before signTypedData
• Adds unit tests for mismatch rejection

AI disclosure

Drafted with AI assistance; reviewed against the Permit2 / blind EIP-712 agent-wallet risk class.

Test plan

• Unit tests for bind helper
• Existing zeroX action tests still pass (mocks)
• CI on this PR

Follow-up tighten (2026-08-05)

• Require domain.chainId; reject wrong/missing domain.name when present
• Exact Permit2 amount match (not ≥)
• Bind message.spender to quote.transaction.to when to is present
• Reject expired deadline
• Expanded unit tests in utils.permit2Bind.test.ts

[cb-heimdall]

🟡 Heimdall Review Status

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[SashaMIT]

Friendly bump — these three tips harden agent spend paths (allowlist matching, Jupiter slippage cap, Permit2 amount + EIP-712 bind). Happy to adjust naming/tests if anything conflicts with your roadmap. Tips are SSH-signed under SashaMIT.