fix(#382): assign unique contract error discriminants

[iyanumajekodunmi756]

Summary

Closes #382.

This PR removes the ContractError discriminant collision between oracle timestamp validation and pending-winnings expiry handling. It also synchronizes the wallet-facing TypeScript error map and documentation with the authoritative Rust enum, and adds a regression test so future duplicate discriminants are caught automatically.

Changes

• Assign PendingWinningsNotExpired the unique stable code 83.
• Preserve OracleTimestampOutsideWindow at code 66.
• Add the missing RotationDelayNotElapsed (55) mapping to TypeScript bindings.
• Move the pending-winnings expiry mapping in the TypeScript decoder from 61 to 83.
• Synchronize docs/WALLET_ERROR_GUIDE.md with every error code currently defined by contracts/src/errors.rs.
• Add a parity regression test asserting that all Rust error discriminants are unique.

Compatibility / migration notes

Contract error codes are part of the client-facing ABI. Existing clients that decode code 61 as PendingWinningsNotExpired must update to code 83. Code 66 now unambiguously identifies OracleTimestampOutsideWindow; clients should not use code 66 for pending-winnings expiry handling.

No contract storage layout, event schema, method signature, or settlement behavior was changed.

Validation

Passed locally:

• node scripts/check-doc-drift.js
• npm --prefix bindings run test:errors
• npm --prefix bindings run build
• npm --prefix bindings run lint
• git diff --check

Rust validation could not be run in the execution environment because cargo is not installed. The existing broader ABI parity command also reports pre-existing contract-method drift unrelated to this issue; the error enum parity portion passes.

Review checklist

• Every ContractError variant has a unique u32 discriminant.
• TypeScript error mapping matches Rust error names and codes.
• Wallet error guide covers the authoritative error map.
• Regression coverage prevents future discriminant collisions.
• No generated build artifacts included.

closes #382