[kawaeeeee]

What

Detect red-light stop-line entry when the physical front bumper crosses the line. For a 4 m vehicle moving from center x = -2.5 m to -1.5 m toward a stop line at x = 0, the bumper moves from -0.5 m to +0.5 m. The current center-based check misses this entry; this change reports the infraction and therefore applies the existing stop-line penalty at that step.

• Sweep both front corners between the previous and current poses, including vehicle width and heading.
• Report one entry event: later crossings by the other front corner, center, or rear do not repeat it.
• Retain the existing red-state, direction, elevation, proximity, and lateral-extension filters.

Why

The current check allows the front of the vehicle to protrude across a red-light stop line without triggering its violation flag or penalty. Front-based entry makes the stopping reference consistent with keeping the vehicle body before the line.

Notes

• 4 bernhard dev #570 introduced a rear-bumper entry event; 6 bernhard dev #580 subsequently changed the reference to the center and cited evaluation-time size inflation. This PR deliberately proposes the physical front bumper. On current 3.0, eval_perceived_size_margin_m changes observations only; the check uses sim_length and sim_width, and a regression test covers that distinction.
• Entering on green and then crossing with the center after the light turns red does not produce a new violation.
• This changes infraction timing and can change rewards, removal timing, and evaluation results for existing policies. Policy retraining was not performed.

Validation:

• Updated red-light suite: 20 test groups pass; 13 groups fail against the original center-based implementation.
• make -C tests/drive test: all C unit and environment smoke suites pass.
• NO_TRAIN=1 python setup.py build_ext --inplace --force and importing the rebuilt pufferlib.ocean.drive.binding: pass in the existing Docker environment.
• clang-format --dry-run --Werror (21.1.5) on both changed C files and git diff --check: pass.