plan: trace tool — multi-PR implementation plan and agent prompts (#243)

* plan: trace tool — multi-PR implementation plan and agent prompts

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* fix review feedback: duplicate test, column header, import contract, hint count, test placement

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: HumanBean17