perf(oracle): encode packed price payloads

[ByteYue]

Summary

Implements the gravity-reth producer half of Galxe/gravity-audit#1092:

• encode the resolver callback as the canonical 32-byte Price Feed V1 word
• normalize Binance Index Price Kline close strings to fixed 8 decimals
• pad short fractions and truncate excess positive fractional digits
• reject signs, whitespace, scientific notation, malformed values, zero, and uint96 overflow
• enforce uint32 round and uint48 timestamp bounds
• retain the existing outer NativeOracle/JWK tuple and closed-bucket semantics
• add exact Solidity-compatible inner and wrapped golden vectors

Golden inner payload:

0100000000000007d101b2e020018e23f2365f0000000000000009543637a800

Dependency

Depends on Galxe/gravity_chain_core_contracts#116, which freezes the matching decoder and one-slot round storage.

The SDK fixtures and E2E/soak suite are intentionally deferred to a separate follow-up PR.

Encoding correction

The existing Alloy call encodes a dynamic tuple value and includes a leading top-level tuple offset. Measured canonical wrapper sizes are therefore:

• old 160-byte callback body: 320-byte wrapper
• new 32-byte callback body: 192-byte wrapper

This corrects the 288 -> 160 estimate in #1092 without changing the existing outer encoding or JWK consensus path.

Polymarket source behavior and production code are unchanged.

Verification

• cargo fmt --all -- --check
• cargo test -p reth-pipe-exec-layer-relayer: 65 passed, 0 failed, 1 external-RPC test ignored
• cargo clippy -p reth-pipe-exec-layer-relayer --all-targets -- -D warnings passes after allowing three unrelated lint classes already present in untouched files
• exact 32-byte inner and 192-byte wrapped golden-vector tests
• round, time, price, decimal, malformed input, and overflow boundary tests