Add a camera calibration tool and a checkerboard to show on a screen

hermes_vision.calibrate collects 20 varied checkerboard views from the camera topic
(rejecting repeats of a pose, which constrain nothing), solves with OpenCV and writes
the camera_info YAML camera_ros loads, named with the resolution as it expects.
Tested: the solver recovers a known synthetic camera (focal length within 1%), the
YAML round-trips, and real board detection works on a rendered board. Not yet run on
the real camera: it needs someone holding a board in front of it, with the focus set.

docs/checkerboard-9x6.png is a 10x7-square board that can be shown on a screen.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AFN8nRRCiDiMN7ChBpHJhs

ros/hermes_vision/setup.py

@@ -21,6 +21,7 @@ setup(
             'face_detector = hermes_vision.face_detector_node:main',
             'detect_faces = hermes_vision.detect_cli:main',
             'people = hermes_vision.people:main',
+            'calibrate = hermes_vision.calibrate:main',
         ],
     },
 )