[HarshRajSinghania]

Summary

Updates the constructor docstring in src/components/obstacle/obstacle.py so that length_m is correctly described as half the obstacle's longitudinal size, matching the existing description for width_m and the actual contour construction (±length_m).

Motivation

Fixes #212. The previous docstring claimed length_m was the full longitudinal size, which is inconsistent with how the outline is built and with the half-size semantics already documented for width_m. Example usage in doc/sensors/visualize_obstacle.py produces a rectangle twice the size of the documented parameters.

Implementation

• Changed only the length_m parameter description in the __init__ docstring from "Obstacle's longitudinal size[m]" to "Half of the obstacle's longitudinal size[m]".
• No code behavior, defaults, or other documentation changed.

Testing

• Verified the change is limited to the docstring (diff is a single line).
• Confirmed the contour construction still uses ±length_m / ±width_m as before.
• No unit tests exist for this class; the change is documentation-only and does not affect runtime behavior.

Closes #212.