Fix/path smoothing robot radius

[ShiboWork]

Reference issue

• fix #1230 Fixes path smoothing safety issue discussed in #1230

What does this implement/fix?

This PR fixes an issue in the path_smoothing() function, where the collision checking via line_collision_check() did not take robot_radius into account correctly. This caused the smoothed path to pass dangerously close to obstacles.

• Modified line_collision_check() to check collision along finite-length line segments and incorporate robot_radius.
• Updated path_smoothing() logic to use this corrected check.
• Added a new unit test to verify that smoothed paths maintain clearance from obstacles based on robot radius.

Additional information

• Confirmed original vs smoothed paths via animation and test assertions.

CheckList

• [x] Did you add an unittest for your new example or defect fix?
• [ ] Did you add documents for your new example? N/A (not a new algorithm)
• [x] All CIs are green? (You can check it after submitting)