[tandede]

Summary

• treat the accepted lower velocity boundary as a constant-velocity zero-blend profile
• add forward and reverse regression coverage

Behaviour change

The accepted zero-blend velocity boundary now returns finite position, velocity and acceleration values instead of NaN/inf. Public signatures are unchanged.

Fixes #924.

Testing

• Focused trajectory tests: 3 passed, 6 subtests passed
• Ruff formatting and focused lint checks on the changed files
• git diff --check

Prepared with substantial assistance from OpenAI Codex (GPT-5); I reviewed and ran the change.

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 0 complexity · 0 duplication

Metric	Results
Complexity	0
Duplication	0

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