feat(actions): implement ActionMapper config-driven gesture→action lookup

merlin/actions/mapper.py

@@ -0,0 +1,20 @@
+"""ActionMapper — translates gesture event names to action names via config."""
+
+from __future__ import annotations
+
+from typing import Optional
+
+from merlin.config import MerlinConfig
+
+
+class ActionMapper:
+    def __init__(self, config: MerlinConfig) -> None:
+        self._mappings = dict(config.mappings)
+
+    def map(self, gesture: str) -> Optional[str]:
+        """Return the action name for a gesture, or None if unmapped."""
+        return self._mappings.get(gesture)
+
+    def reload(self, config: MerlinConfig) -> None:
+        """Replace mappings from a new config (e.g. after user edits in UI)."""
+        self._mappings = dict(config.mappings)

tests/test_actions/test_mapper.py

@@ -0,0 +1,28 @@
+from merlin.actions.mapper import ActionMapper
+from merlin.config import MerlinConfig
+
+
+def test_maps_known_gesture():
+    config = MerlinConfig()
+    mapper = ActionMapper(config)
+    assert mapper.map("left_blink") == "left_click"
+
+
+def test_returns_none_for_unknown_gesture():
+    config = MerlinConfig()
+    mapper = ActionMapper(config)
+    assert mapper.map("nonexistent_gesture") is None
+
+
+def test_custom_mapping_overrides_default():
+    config = MerlinConfig(mappings={"left_blink": "key_enter"})
+    mapper = ActionMapper(config)
+    assert mapper.map("left_blink") == "key_enter"
+
+
+def test_reload_picks_up_new_config():
+    config = MerlinConfig()
+    mapper = ActionMapper(config)
+    config.mappings["head_nod"] = "double_click"
+    mapper.reload(config)
+    assert mapper.map("head_nod") == "double_click"