fix: stop swallowing facilitator verification errors

[namedfarouk]

Summary

This PR fixes silent catch behavior in facilitator verification flows so we no longer continue with ambiguous state when core checks fail.

What changed

• EVM exact verifyEIP3009:
  • log signature verification exceptions with context
  • return explicit invalid_exact_evm_payload_signature_verification_error when smart-wallet bytecode lookup fails
  • return explicit invalid_exact_evm_payload_balance_check_failed when balance reads fail
  • keep fallback logic for undeployed smart wallets but avoid silent parse failures
• EVM exact verifyPermit2:
  • log signature verification exceptions and return invalid_permit2_signature_verification_error
  • return explicit permit2_allowance_check_failed on allowance read errors
  • return explicit permit2_balance_check_failed on balance read errors
• SVM exact facilitator verify flow:
  • log transaction decode and transfer parse failures with context
  • return explicit invalid_exact_svm_payload_recipient_ata_lookup_failed (with message) when ATA derivation fails instead of generic recipient mismatch

Tests

Added targeted regression coverage in:

• typescript/packages/mechanisms/evm/test/unit/exact/facilitator.test.ts

Validated with:

• pnpm --filter @x402/evm test -- test/unit/exact/facilitator.test.ts
• pnpm --filter @x402/svm test -- test/unit/facilitator.test.ts

Fixes #13