[jadenfix]

Add Encode and Decode implementations for core::ops::Bound<T> to support transmitting range bounds, as requested in #122.

The three variants use the existing validated variant and payload codecs, following the Result implementation. No new unsafe code or Clone/Default requirement on T is introduced. The representation matches a derived enum with Included(T), Excluded(T), and Unbounded; no_std and borrowed payload decoding work.

Tests cover all variants, empty and 300-element vectors, reusable buffers, borrowed strings, non-Clone payloads, malformed Unicode, truncated/trailing input, and the derived-enum wire oracle. The public consumer failed to compile on main and now passes 25 range-request serialize/decode/query journeys with default features disabled.

Validation:

• Default: 214 tests and 6 doctests pass (1 ignored).
• All features: 242 tests and 6 doctests pass (1 ignored).
• Documented no-std feature configuration: 232 tests and 6 doctests pass.
• Full all-feature Miri: 241 tests and 6 doctests pass (1 ignored), using current nightly with strict provenance. The five new tests also pass under 32-bit i686 and big-endian PowerPC64 Miri.
• Exact MSRV 1.88 default/minimal library checks, formatting, and strict documentation build pass.

The pinned upstream nightly, native Linux cross-target matrix, and upstream CI fuzz command were not executed locally. Optional current-nightly Clippy completes with existing diagnostics outside the new module. A separate AI reviewer checked the final commit and independently reran the five new tests. Prepared with AI assistance.

Closes #122.