Consolidate poc-memory and poc-agent configs

poc-memory now reads from poc-agent's config.json5 as the primary
config source. Memory-specific settings live in a "memory" section;
API credentials are resolved from the shared model/backend config
instead of being duplicated.

- Add "memory" section to ~/.config/poc-agent/config.json5
- poc-memory config.rs: try shared config first, fall back to
  legacy JSONL
- API fields (base_url, api_key, model) resolved via
  memory.agent_model -> models -> backend lookup
- Add json5 dependency for proper JSON5 parsing
- Update provisioning scripts: hermes -> qwen3_coder tool parser

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/provision-mi300x.sh

@@ -81,8 +81,8 @@ exec vllm serve "$MODEL" \
     --max-model-len "$MAX_MODEL_LEN" \
     --gpu-memory-utilization "$GPU_MEMORY_UTILIZATION" \
     --enable-prefix-caching \
-    --tool-call-parser hermes \
     --enable-auto-tool-choice \
+    --tool-call-parser qwen35_coder \
     --reasoning-parser qwen3 \
     --trust-remote-code \
     --max-cudagraph-capture-size 64 \