docs: tighten clickthrough skill and API guidance

Closes #10

docs/API.md

@@ -76,6 +76,11 @@ Default response returns cropped image + region metadata in global pixel coordin
 
 Body: one action.
 
+Important:
+- the request body uses `action` plus an optional `target`
+- pixel coordinates live inside `target` when `target.mode="pixel"`
+- do **not** send top-level `x` / `y` fields
+
 Query params:
 
 - `screen` (int, default `0`) - zero-based display selector included in the response metadata; invalid values fall back to `0`
@@ -170,6 +175,25 @@ Hotkey:
 }
 ```
 
+Right click:
+
+```json
+{
+  "action": "right_click",
+  "target": {"mode": "pixel", "x": 1300, "y": 740}
+}
+```
+
+Move only:
+
+```json
+{
+  "action": "move",
+  "target": {"mode": "pixel", "x": 1300, "y": 740},
+  "duration_ms": 150
+}
+```
+
 ## `POST /ocr`
 
 Extract visible text from either a full screenshot, a region crop, or caller-provided image bytes.