feat: arbiter v2 — 10-feature expansion

Merged 5 feature branches implementing:
- Blob loader completion + runtime hot-swap + model versioning (REQ-ARCH-034/041)
- Python evaluator + arbiterc eval CLI (REQ-ARCH-035)
- Event-driven evaluation (REQ-ARCH-036)
- Multi-model composition with shared fact bus (REQ-ARCH-037)
- Remote trace export with pluggable transport (REQ-ARCH-038)
- State machine support in ARB language (REQ-ARCH-039)
- Hardware benchmark configs for STM32F4/H7 (REQ-ARCH-040)
- Zbus integration + Grafana metrics via Zephyr STATS (REQ-ARCH-042)
- MISRA-C analysis CI + stack usage reporting (REQ-BUILD-003)

141 tests passing (55 new evaluator tests + existing suite).

Co-Authored-By: Oz <oz-agent@warp.dev>

Author: tbitcs

python/arbiter/emit_blob.py

@@ -278,6 +278,7 @@ def _pack_strings(model: CanonicalModel) -> tuple[bytes, list[int]]:
     seen: dict[str, int] = {}
 
     def _add(s: str | None) -> int:
+        nonlocal buf
         if s is None:
             return 0xFFFF
         if s in seen: