CV Calibrate Camera (Circle Grid)

Estimates a camera's intrinsics and lens distortion from several circle-grid views (cv2.calibrateCamera). Calibration needs per-view 2D/3D correspondences accumulated across images, which the raw wrappers can't express, so this node manages it exactly like the chessboard 'Calibrate Camera': feed an IMAGE BATCH of circle-grid photos from DIFFERENT angles; each is grayscaled, its circle centers are found with cv2.findCirclesGrid and matched to planar object points built from pattern size x square_size. Views where the grid is not found are skipped. The 'asymmetric (staggered)' layout is the usual choice - it is the OpenCV-recommended calibration target for wide-angle and stereo rigs, since the staggered rows break the 180-degree ambiguity that plagues symmetric grids. Failure-tolerant: with fewer than 3 usable views it returns found=false, an identity matrix and zero distortion. Feed camera_matrix + dist_coeffs into cv2.undistort, or into 'Stereo Calibrate (Circle Grid)' as initial guesses; rms_error (px) reports fit quality (under ~1 is good).