feat(automation): select op — target entities by handle/type/layer

Add a select op that sets the document selection (by hex handles from
query, or by type/layer, or clear). Selection drives modify commands, so
an agent can query → select → run("ERASE") to act on specific entities.
Completes the modify half of the act/observe loop. ocs.py gains select().

Co-Authored-By: Claude Opus 4.8 <[email protected]>

docs/automation/README.md

@@ -20,8 +20,18 @@ can act → observe → act.
 | `{"op":"run","cmd":"LAYER Walls"}` | `{"ok":true,"cmd":...,"entities":N,"added":D}` |
 | `{"op":"entities"}` | `{"ok":true,"total":N,"by_type":{"Line":42,...}}` |
 | `{"op":"query","type":"Line","layer":"Walls"}` | per-entity `{handle,type,layer,…geometry}` (filters + `limit` optional) |
+| `{"op":"select","handles":["2B"]}` | set the selection (by `handles`, `type`, or `layer`; `clear` to deselect) → `{"ok":true,"selected":N}` |
 | `{"op":"save","path":"out.dwg"}` | `{"ok":true,"saved":"out.dwg"}` (path optional once opened/saved) |
 
+Selection drives modify commands — `select` the targets (e.g. the handles a
+`query` returned), then `run("ERASE")`:
+
+```python
+ocs.select(type="Line"); ocs.run("ERASE")   # erase every line
+ids = [e["handle"] for e in ocs.query(layer="Walls")["entities"]]
+ocs.select(handles=ids); ocs.run("ERASE")
+```
+
 Every response has `"ok"`; failures carry `"error"`. `run` drives Open CAD
 Studio's **own** command system — no separate bindings to maintain — so its
 coverage grows with the app.

docs/automation/ocs.py

@@ -79,6 +79,19 @@ class Ocs:
         """List entities (handle, type, layer, geometry), optionally filtered."""
         return self._send(op="query", type=type, layer=layer, limit=limit)
 
+    def select(
+        self,
+        handles: Optional[list[str]] = None,
+        type: Optional[str] = None,
+        layer: Optional[str] = None,
+        clear: bool = False,
+    ) -> dict[str, Any]:
+        """Set the selection by handle, type, or layer (a following selection
+        command like ``run("ERASE")`` then acts on it). `clear=True` deselects."""
+        return self._send(
+            op="select", handles=handles, type=type, layer=layer, clear=clear
+        )
+
     def save(self, path: Optional[str] = None) -> dict[str, Any]:
         """Write the document (defaults to the opened/last-saved path)."""
         return self._send(op="save", path=path)