Add annotation tool for valve handle orientation

[kluge7]

Task:

• Build a small tool to extend the current dataset with handle orientation annotations.
• Current label format (YOLO default, from Roboflow):

<class_id> <x_center> <y_center> <width> <height>

Example:

0 0.512 0.478 0.220 0.330

• Proposed expanded format (with orientation θ):

<class_id> <x_center> <y_center> <width> <height> <theta>

Example:

0 0.512 0.478 0.220 0.330 1.5708

• Required functionality::
  • Load image with its bounding box (Roboflow export).
  • User draws a line along the valve handle.
  • Tool calculates orientation angle θ (in radians, CCW).
  • Save angle alongside bbox in the updated label file.
• Keep it lightweight (Python + OpenCV or Matplotlib GUI is fine).

Angle convention (must be consistent)

• 0° / 0 rad -> Valve handle pointing upwards (Shut position).
• 90° / π/2 rad -> Valve handle pointing left (Open position).
• Rotation is counterclockwise (CCW) from Shut -> Open.

For example, in the image below the handle is vertical: θ = 0 rad (0°)

Deliverables:

• Simple GUI tool or script for manual angle annotation.
• Updated dataset format: bbox + θ.
• Documentation:
  • How to use the tool.
  • Example of annotated label files before/after.

References:

• OpenCV drawing functions
• Matplotlib interactive events
• Roboflow custom annotation docs
• Roboflow download example (see Step 1 in train.py for how to fetch images + YOLO Labels from Roboflow)