[GrantFox] Stabilize public error mapping (#1380)

[s6pa1rta3n-lab]

Summary

Closes #1380.

Stabilizes public error mapping across all contract variants, ensures non-colliding client code allocations, safe decoding for unknown error codes, and adds comprehensive golden vector integration test coverage.

Acceptance Criteria Checklist

• Existing codes remain stable: All 116 existing client code mappings and discriminant values are preserved without modification.
• New codes are unique and documented: All unmapped enum Error variants (16 new variants) have been assigned unique, non-colliding client codes in their respective domain bands and fully documented.
• Unknown values decode safely: Error::decode_contract_code and Error::decode_client_code safely decode unknown/out-of-range integer values to PublicErrorMapping with is_known: false and fallback defaults ("UNKNOWN_ERROR").
• Golden vectors cover public entrypoints: test_golden_vectors in error_code_tests.rs provides explicit coverage across Authentication, Market Lifecycle, Betting/Financial, Validation, Circuit Breaker, and Dispute resolution entrypoints.

Changes Included

• contracts/predictify-hybrid/src/err.rs:
  • Defined PublicErrorMapping metadata structure.
  • Implemented exhaustive public_mapping(&self), from_contract_code, from_client_code, from_code_str, decode_contract_code, and decode_client_code functions covering all 132 Error variants.
• contracts/predictify-hybrid/src/error_code_tests.rs:
  • Added unit test suite covering uniqueness, range validity, round-trip parsing, safe decoding of unknown values, and golden vector entrypoints.
• contracts/predictify-hybrid/src/lib.rs:
  • Enabled mod error_code_tests; for test builds.
• Upstream compilation repairs:
  • types.rs: Added Eq, PartialEq to BetStats.
  • admin.rs & validation.rs: Fixed ConfigValidator and OracleConfigValidator calls.
  • event_topic_compat_tests.rs: Added use alloc::format;.

Payout Routing

• EVM (Base/Arbitrum/Polygon/ETH): 0xF46C9F6d70C50BF81ef3588AB523a90a594a2F89
• Stellar: GCL6OXAMLD75BMTINA6EMRUDWK5THQUSHMYNLSNBCJAPZJHNYJTUNIBC