[Feature]: Geometry-aware dispatch to stop the recurring "silent AABB" bug class

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Feature Description

What: A small geometry-aware dispatch layer so detection ops use the geometry each detection actually carries (mask / OBB / box) instead of silently falling back to the axis-aligned xyxy.

Why: Several recent fixes are the same bug in different functions: code grabs detections.xyxy and forgets the real geometry lives in data["xyxyxyxy"] (OBB) or mask. Because xyxy is always present, the wrong answer is the silent default:

• Detections.area returned the AABB area, not the rotated body (#2306)
• with_nms / with_nmm dropped crossed OBBs via AABB IoU (#2303)
• as_yolo dropped OBB rotation on export (#2289)
• roboflow/inference: consensus IoU, and stitch / crop corner shifts (https://github.com/roboflow/inference/pull/2420, https://github.com/roboflow/inference/pull/2427, https://github.com/roboflow/inference/pull/2430)

Same root cause each time: Detections holds several geometries at once and xyxy is just a derived envelope, so every consumer re-implements "which geometry is the real one?" and forgetting it fails silently. The next geometry-aware function will hit it again.

How: Centralize the dispatch into a few batched helpers and route call sites through them instead of reaching for xyxy. No data-model change, keeps the vectorized design, backward compatible. Migration can be incremental, then deprecate the ad-hoc paths.

Proposed helpers (batched, no per-detection loops):

• detection_iou(a, b): dispatches mask / OBB / box IoU
• detection_area(det): mask sum / shoelace / box area
• move_detections(det, offset): shifts xyxy, mask, OBB corners and keypoints together (what #2427 / #2430 each forgot)
• a test_op_respects_geometry contract test that fails when an op can't tell an OBB from its envelope

Rollout can be incremental and each step is independent / backward compatible: (1) consolidate the duplicated move_detections (pure dedup, no behavior change), (2) the read-only detection_iou / detection_area dispatch, (3) the contract test.

A first pass suggests more call sites in the same class worth investigating: get_anchors_coordinates (and therefore LineZone / PolygonZone) reads anchors off the envelope rather than the rotated body, as_coco and as_pascal_voc have no is_obb option and drop the rotation on export, with_nmm merges to the union envelope while keeping one input's data["xyxyxyxy"], and DetectionsSmoother averages xyxy without smoothing the oriented corners.

Example Usage

# one dispatch per op, instead of every function re-deriving it
def detection_area(det):
    if det.mask is not None:        return det.mask.sum(axis=(1, 2))
    if "xyxyxyxy" in det.data:      return _shoelace(det.data["xyxyxyxy"])
    return box_area(det.xyxy)

# same shape for detection_iou (mask / OBB / box), plus a geometry-complete
# move_detections that shifts every geometry field together (what #2427/#2430 forgot)

# and a contract test so the class is loud, not silent:
assert op(obb) != op(aabb_of(obb))   # an op must tell an OBB from its envelope

Are you willing to submit a PR?

• Yes I'd like to help by submitting a PR!