feat: integrate canonical Deepstate settlement on Robinhood Chain

[dangerousfood]

Summary

Integrates Deepstate into 0x Settler on Robinhood Chain using the same production deployment and settlement model as the LI.FI integration.

• expose a DEEPSTATE self-funded action only through RobinHoodMixin
• pin the canonical Robinhood Chain engine at 0x6cf19308C22FC82ea620Fa0B3E94948d20f27B96
• use 0x ppm semantics and the signed transaction buy token, recipient, and final slippage check
• require every fill to use the declared direct market and direction with sorted token addresses
• force every leg to noRest
• cap ERC-20 authority with an exact temporary approval and clear it after settlement
• reject non-exact input accounting, including fee-on-transfer/rebasing behavior
• refund only the selected but unmatched input to the signed recipient while retaining the unselected balance for later actions
• support ERC-20 and native input/output without forwarding unrelated native balance
• keep the action unavailable on all non-Robinhood Settlers

Verification

• Deepstate unit suite: 14/14 passed
• bounded ERC-20 spend fuzzing: 100,000 runs passed
• live Robinhood fork at block 48,052,050: passed against the deployed engine
  • real resting maker order created and consumed
  • live 10 bps protocol fee verified
  • unmatched input refunded
  • taker remainder did not rest
  • no Settler token residue
  • temporary allowance cleared
• broader local unit/FV/invariant coverage: 115 tests passed, including a 20,000-call Uniswap V4 invariant run
• RobinHoodSettler size: 22,904 bytes (1,672 bytes below EIP-170)
• Deepstate execution gas snapshot: 205,054 gas
• production builds: passed
• VIP/action selector collision check: passed
• existing gas snapshot comparison: no regressions
• scoped Foundry lint, formatting, and diff checks: passed
• npm audit: 0 vulnerabilities

Upstream base

Based on current 0xProject/0x-settler@1df90874.

[dangerousfood]

Superseded by #3, which adds the final Settler-native security boundaries and preserves the reviewed implementation as one commit without rewriting history.