feat(compression): add summary_base_url + move compression config to YAML-only

- Add summary_base_url config option to compression block for custom
  OpenAI-compatible endpoints (e.g. zai, DeepSeek, Ollama)
- Remove compression env var bridges from cli.py and gateway/run.py
  (CONTEXT_COMPRESSION_* env vars no longer set from config)
- Switch run_agent.py to read compression config directly from
  config.yaml instead of env vars
- Fix backwards-compat block in _resolve_task_provider_model to also
  fire when auxiliary.compression.provider is 'auto' (DEFAULT_CONFIG
  sets this, which was silently preventing the compression section's
  summary_* keys from being read)
- Add test for summary_base_url config-to-client flow
- Update docs to show compression as config.yaml-only

Closes #1591
Based on PR #1702 by @uzaylisak

run_agent.py

@@ -837,10 +837,17 @@ class AIAgent:
         
         # Initialize context compressor for automatic context management
         # Compresses conversation when approaching model's context limit
-        # Configuration via config.yaml (compression section) or environment variables
-        compression_threshold = float(os.getenv("CONTEXT_COMPRESSION_THRESHOLD", "0.50"))
-        compression_enabled = os.getenv("CONTEXT_COMPRESSION_ENABLED", "true").lower() in ("true", "1", "yes")
-        compression_summary_model = os.getenv("CONTEXT_COMPRESSION_MODEL") or None
+        # Configuration via config.yaml (compression section)
+        try:
+            from hermes_cli.config import load_config as _load_compression_config
+            _compression_cfg = _load_compression_config().get("compression", {})
+            if not isinstance(_compression_cfg, dict):
+                _compression_cfg = {}
+        except ImportError:
+            _compression_cfg = {}
+        compression_threshold = float(_compression_cfg.get("threshold", 0.50))
+        compression_enabled = str(_compression_cfg.get("enabled", True)).lower() in ("true", "1", "yes")
+        compression_summary_model = _compression_cfg.get("summary_model") or None
         
         self.context_compressor = ContextCompressor(
             model=self.model,