Add opt-in integrator taker fees

[dangerousfood]

Summary

• add opt-in fillWithIntegratorFee and fillRouteWithIntegratorFee entrypoints
• calculate integrator fees independently from the same per-leg gross matched output and floor rounding as the protocol taker fee
• cap integrator fees at 100 bps and leave rests, cancels, and maker claims fee-free
• preserve every legacy entrypoint, storage field, and radix matching function unchanged
• support ERC20 and native ETH settlement, per-token route consolidation, and atomic rollback

Verification

• 381 non-invariant tests passed
• 38 stateful invariant properties passed at 256 runs x 64 calls
• adjusted 100% line, statement, branch, and function coverage
• 1,253 complete-domain SMT obligations passed
• 26 Halmos symbolic tests passed
• Slither: 80 detectors, 0 findings
• production runtime: 22,321 bytes, 2,255-byte EIP-170 margin
• isolated integrator-fee gas snapshots checked in CI

Fee semantics

For each matched route leg, protocol and integrator fees are each floor(grossMatchedOutput * bps / 10_000). Both use the original gross output, so neither fee compounds on the other. Caller settlement occurs first, followed by protocol fees, integrator fees, and any excess native-ETH refund.