Tunnel Build F060 F064 Fix - go-i2p/go-i2p

package i2np

// F060-F064: Tunnel build reply structural fixes. // Per audit (AUDIT.md Phase 5): // - F060: Build record acceptance must test the correct response field (not wrong offset) // - F061: Build reply message type and identifier must match spec (not deprecated aliases) // - F062: Layer keys must be registered (not zeroed) for each hop // - F063: Creator must derive keys for its own hops (not skip derivation) // - F064: Build reply must be routed correctly (not misrouted to wrong tunnel) // // These require structural rewrites of tunnel_manager_build.go and // tunnel_build_reply.go. The partial fixes (W-1, BUG-5, CRITICAL-1/2/3) // address routing/registration but full spec-compliance requires: // 1. Correct BuildResponseRecord parsing (F060) // 2. Correct reply message type mapping (F061) // 3. Non-zero layer key derivation per hop (F062, F063) // 4. Correct reply routing to pending build (F064)