_get_ollama_model() used prefix match (startswith) on /api/tags,
causing qwen3:30b to match qwen3.5:latest. Now:
1. Queries /api/ps (loaded models) first — most accurate
2. Falls back to /api/tags with exact name match
3. Reports actual running model, not just configured one
Updated test_get_system_info_contains_model to not assume model==config.
Fixes#77. 5 regression tests added.