feat: add TokenReader for plain/compressed delta token dispatch

[oferchen]

Summary

• Implement Strategy pattern for reading delta tokens in both plain (4-byte LE i32) and compressed (DEFLATED_DATA) wire formats
• Mirrors upstream recv_token() dispatch from token.c:271
• Includes 13 unit tests covering roundtrips, block references, EOF, and edge cases

Test plan

• Unit tests in module pass
• cargo fmt passes