feat(agents): add configurable DeepSeek Harness model catalog

- Separate default model selection from catalog configuration
- Use API metadata with per-model and provider overrides
- Expose documented capability, reasoning, protocol, and request settings
- Preserve customizations with conflict detection and transactional rollback

src-tauri/src/tests.rs

@@ -1,6 +1,7 @@
 use super::*;
 
 mod agent_configuration;
+mod deepseek_harness_catalog;
 mod agent_paths;
 mod agent_state;
 mod agent_transactions;