feat(honcho): scope host and peer resolution to active Hermes profile

Derives the Honcho host key from the active Hermes profile so that each
profile gets its own Honcho host block, workspace, and AI peer identity.

Profile "coder" resolves to host "hermes.coder", reads from
hosts["hermes.coder"] in honcho.json, and defaults workspace + aiPeer
to the derived host name.

Resolution order: HERMES_HONCHO_HOST env var > active profile name >
"hermes" (default).

Complements #3681 (profiles) with the Honcho identity layer that was
part of #2845 (named instances), adapted to the merged profiles system.

tests/honcho_integration/test_client.py

@@ -11,6 +11,7 @@ from honcho_integration.client import (
     HonchoClientConfig,
     get_honcho_client,
     reset_honcho_client,
+    resolve_active_host,
     resolve_config_path,
     GLOBAL_CONFIG_PATH,
     HOST,
@@ -372,6 +373,101 @@ class TestResolveConfigPath:
         assert config.workspace_id == "local-ws"
 
 
+class TestResolveActiveHost:
+    def test_default_returns_hermes(self):
+        with patch.dict(os.environ, {}, clear=True):
+            os.environ.pop("HERMES_HONCHO_HOST", None)
+            os.environ.pop("HERMES_HOME", None)
+            assert resolve_active_host() == "hermes"
+
+    def test_explicit_env_var_wins(self):
+        with patch.dict(os.environ, {"HERMES_HONCHO_HOST": "hermes.coder"}):
+            assert resolve_active_host() == "hermes.coder"
+
+    def test_profile_name_derives_host(self):
+        with patch.dict(os.environ, {}, clear=False):
+            os.environ.pop("HERMES_HONCHO_HOST", None)
+            with patch("hermes_cli.profiles.get_active_profile_name", return_value="coder"):
+                assert resolve_active_host() == "hermes.coder"
+
+    def test_default_profile_returns_hermes(self):
+        with patch.dict(os.environ, {}, clear=False):
+            os.environ.pop("HERMES_HONCHO_HOST", None)
+            with patch("hermes_cli.profiles.get_active_profile_name", return_value="default"):
+                assert resolve_active_host() == "hermes"
+
+    def test_custom_profile_returns_hermes(self):
+        with patch.dict(os.environ, {}, clear=False):
+            os.environ.pop("HERMES_HONCHO_HOST", None)
+            with patch("hermes_cli.profiles.get_active_profile_name", return_value="custom"):
+                assert resolve_active_host() == "hermes"
+
+    def test_profiles_import_failure_falls_back(self):
+        import importlib
+        import sys
+        with patch.dict(os.environ, {}, clear=False):
+            os.environ.pop("HERMES_HONCHO_HOST", None)
+            # Temporarily remove hermes_cli.profiles to simulate import failure
+            saved = sys.modules.get("hermes_cli.profiles")
+            sys.modules["hermes_cli.profiles"] = None  # type: ignore
+            try:
+                assert resolve_active_host() == "hermes"
+            finally:
+                if saved is not None:
+                    sys.modules["hermes_cli.profiles"] = saved
+                else:
+                    sys.modules.pop("hermes_cli.profiles", None)
+
+
+class TestProfileScopedConfig:
+    def test_from_env_uses_profile_host(self):
+        with patch.dict(os.environ, {"HONCHO_API_KEY": "key"}):
+            config = HonchoClientConfig.from_env(host="hermes.coder")
+        assert config.host == "hermes.coder"
+        assert config.workspace_id == "hermes.coder"
+        assert config.ai_peer == "hermes.coder"
+
+    def test_from_env_default_workspace_preserved_for_default_host(self):
+        with patch.dict(os.environ, {"HONCHO_API_KEY": "key"}):
+            config = HonchoClientConfig.from_env(host="hermes")
+        assert config.host == "hermes"
+        assert config.workspace_id == "hermes"
+
+    def test_from_global_config_reads_profile_host_block(self, tmp_path):
+        config_file = tmp_path / "config.json"
+        config_file.write_text(json.dumps({
+            "apiKey": "shared-key",
+            "hosts": {
+                "hermes": {"aiPeer": "hermes", "peerName": "alice"},
+                "hermes.coder": {
+                    "aiPeer": "hermes.coder",
+                    "peerName": "alice-coder",
+                    "workspace": "coder-ws",
+                },
+            },
+        }))
+        config = HonchoClientConfig.from_global_config(
+            host="hermes.coder", config_path=config_file,
+        )
+        assert config.host == "hermes.coder"
+        assert config.workspace_id == "coder-ws"
+        assert config.ai_peer == "hermes.coder"
+        assert config.peer_name == "alice-coder"
+
+    def test_from_global_config_auto_resolves_host(self, tmp_path):
+        config_file = tmp_path / "config.json"
+        config_file.write_text(json.dumps({
+            "apiKey": "key",
+            "hosts": {
+                "hermes.dreamer": {"peerName": "dreamer-user"},
+            },
+        }))
+        with patch("honcho_integration.client.resolve_active_host", return_value="hermes.dreamer"):
+            config = HonchoClientConfig.from_global_config(config_path=config_file)
+        assert config.host == "hermes.dreamer"
+        assert config.peer_name == "dreamer-user"
+
+
 class TestResetHonchoClient:
     def test_reset_clears_singleton(self):
         import honcho_integration.client as mod