fix(honcho): migration guard for observation mode default change

Existing honcho.json configs without an explicit observationMode now
default to 'unified' (the old default) instead of being silently
switched to 'directional'. New installations get 'directional' as
the new default.

Detection: _explicitly_configured (host block exists or enabled=true)
signals an existing config. When true and no observationMode is set
anywhere in the config chain, falls back to 'unified'. When false
(fresh install), uses 'directional'.

Users who explicitly set observationMode or granular observation
booleans are unaffected — explicit config always wins.

5 new tests covering all migration paths.

tests/honcho_plugin/test_client.py

@@ -437,6 +437,69 @@ class TestProfileScopedConfig:
         assert config.peer_name == "dreamer-user"
 
 
+class TestObservationModeMigration:
+    """Existing configs without explicit observationMode keep 'unified' default."""
+
+    def test_existing_config_defaults_to_unified(self, tmp_path):
+        """Config with host block but no observationMode → 'unified' (old default)."""
+        cfg_file = tmp_path / "config.json"
+        cfg_file.write_text(json.dumps({
+            "apiKey": "k",
+            "hosts": {"hermes": {"enabled": True, "aiPeer": "hermes"}},
+        }))
+        cfg = HonchoClientConfig.from_global_config(config_path=cfg_file)
+        assert cfg.observation_mode == "unified"
+
+    def test_new_config_defaults_to_directional(self, tmp_path):
+        """Config with no host block and no credentials → 'directional' (new default)."""
+        cfg_file = tmp_path / "config.json"
+        cfg_file.write_text(json.dumps({}))
+        cfg = HonchoClientConfig.from_global_config(config_path=cfg_file)
+        assert cfg.observation_mode == "directional"
+
+    def test_explicit_directional_respected(self, tmp_path):
+        """Existing config with explicit observationMode → uses what's set."""
+        cfg_file = tmp_path / "config.json"
+        cfg_file.write_text(json.dumps({
+            "apiKey": "k",
+            "hosts": {"hermes": {"enabled": True, "observationMode": "directional"}},
+        }))
+        cfg = HonchoClientConfig.from_global_config(config_path=cfg_file)
+        assert cfg.observation_mode == "directional"
+
+    def test_explicit_unified_respected(self, tmp_path):
+        """Existing config with explicit observationMode unified → stays unified."""
+        cfg_file = tmp_path / "config.json"
+        cfg_file.write_text(json.dumps({
+            "apiKey": "k",
+            "observationMode": "unified",
+            "hosts": {"hermes": {"enabled": True}},
+        }))
+        cfg = HonchoClientConfig.from_global_config(config_path=cfg_file)
+        assert cfg.observation_mode == "unified"
+
+    def test_granular_observation_overrides_preset(self, tmp_path):
+        """Explicit observation object overrides both preset and migration default."""
+        cfg_file = tmp_path / "config.json"
+        cfg_file.write_text(json.dumps({
+            "apiKey": "k",
+            "hosts": {"hermes": {
+                "enabled": True,
+                "observation": {
+                    "user": {"observeMe": True, "observeOthers": False},
+                    "ai": {"observeMe": False, "observeOthers": True},
+                },
+            }},
+        }))
+        cfg = HonchoClientConfig.from_global_config(config_path=cfg_file)
+        # observation_mode falls back to "unified" (migration), but
+        # granular booleans from the observation object win
+        assert cfg.user_observe_me is True
+        assert cfg.user_observe_others is False
+        assert cfg.ai_observe_me is False
+        assert cfg.ai_observe_others is True
+
+
 class TestResetHonchoClient:
     def test_reset_clears_singleton(self):
         import plugins.memory.honcho.client as mod