[nick2781]

Adds a reusable Protobuf boundary for owning nested Entity baselines and deltas. Applications supply a fixed trusted projection; the codec preserves typed values, row incarnations and container replacement/patch semantics while rejecting duplicate indexed records and enforcing separate wire, state and patch limits. Existing scalar APIs and the current room contract remain unchanged in this PR.

Preserves the caller's Win32 GetMessage macro around Protobuf declarations and codec implementation. The collision was reproduced locally before the fix; hosted Windows acceptance remains required.

Includes public header mappings, consumer wiring and bilingual API documentation. The room/Godot integration follows separately.

Makes lifecycle boundary tests select their expiry inside the target hook instead of requiring preceding trace writes and scheduling to finish within 50 ms. Resource-retention assertions and separate real-time CLI coverage remain in place.

Validation:

• Permanent check-nested-wire: GUID64 13 cases / 122 assertions; GUID32 13 cases / 123 assertions, including both Win32 GetMessage macro/include orders.
• clang-format 18 full tracked-file check and git diff checks passed.
• Nimbus build/link checks passed; both new protocol pages verified in HTML, canonical Markdown and AI output.
• Deterministic launcher boundary cases, the application lifecycle/CLI suite and core runtime regressions passed. A controlled earlier-hook delay reproduces the old test failure; the repaired test passes under the same delay and rejects a missing post-hook deadline check.

These checks cover the codec and its bounds, not client transport, deployment capacity or production qualification.