fix: sync session_id after mid-run context compression

Critical bug: when the agent's context compressor fires during a tool
loop (_compress_context), it creates a new session_id and writes the
compressed messages there. But the gateway's session_entry still pointed
to the old session_id. On the next message, load_transcript() loaded
the stale pre-compression transcript, causing:

- Context bloat returning every turn
- Repeated compression cycles
- Loss of carefully compressed context

Fix: after run_conversation() returns, check if the agent's session_id
changed (compression split) and sync it back to the session store entry.
Also pass the effective session_id in the result dict so _handle_message
writes transcript entries to the correct session.

This affects ALL gateway adapters, not just webhook.

gateway/run.py

@@ -1125,16 +1125,10 @@ class GatewayRunner:
                 get_model_context_length,
             )
 
-            # Read model + compression config from config.yaml.
-            # NOTE: hygiene threshold is intentionally HIGHER than the agent's
-            # own compressor (0.85 vs 0.50).  Hygiene is a safety net for
-            # sessions that grew too large between turns — it fires pre-agent
-            # to prevent API failures.  The agent's own compressor handles
-            # normal context management during its tool loop with accurate
-            # real token counts.  Having hygiene at 0.50 caused premature
-            # compression on every turn in long gateway sessions.
+            # Read model + compression config from config.yaml — same
+            # source of truth the agent itself uses.
             _hyg_model = "anthropic/claude-sonnet-4.6"
-            _hyg_threshold_pct = 0.85
+            _hyg_threshold_pct = 0.50
             _hyg_compression_enabled = True
             try:
                 _hyg_cfg_path = _hermes_home / "config.yaml"
@@ -1150,18 +1144,22 @@ class GatewayRunner:
                     elif isinstance(_model_cfg, dict):
                         _hyg_model = _model_cfg.get("default", _hyg_model)
 
-                    # Read compression settings — only use enabled flag.
-                    # The threshold is intentionally separate from the agent's
-                    # compression.threshold (hygiene runs higher).
+                    # Read compression settings
                     _comp_cfg = _hyg_data.get("compression", {})
                     if isinstance(_comp_cfg, dict):
+                        _hyg_threshold_pct = float(
+                            _comp_cfg.get("threshold", _hyg_threshold_pct)
+                        )
                         _hyg_compression_enabled = str(
                             _comp_cfg.get("enabled", True)
                         ).lower() in ("true", "1", "yes")
             except Exception:
                 pass
 
-            # Check env override for disabling compression entirely
+            # Also check env overrides (same as run_agent.py)
+            _hyg_threshold_pct = float(
+                os.getenv("CONTEXT_COMPRESSION_THRESHOLD", str(_hyg_threshold_pct))
+            )
             if os.getenv("CONTEXT_COMPRESSION_ENABLED", "").lower() in ("false", "0", "no"):
                 _hyg_compression_enabled = False