同一Issue/MR/PRの過去コンテキスト引き継ぎ機能 詳細設計書 (#101)

* Initial plan

* Add context inheritance specification with Planning Mode support

Co-authored-by: notfolder <20558197+notfolder@users.noreply.github.com>

* Address code review feedback: improve documentation clarity

Co-authored-by: notfolder <20558197+notfolder@users.noreply.github.com>

* Address review feedback: simplify context inheritance specification

Co-authored-by: notfolder <20558197+notfolder@users.noreply.github.com>

* Improve specification clarity based on internal code review

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* Update CONTEXT_INHERITANCE_SPECIFICATION.md

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Co-authored-by: notfolder <20558197+notfolder@users.noreply.github.com>
Co-authored-by: notfoler <notfolder@gmail.com>

Author: Copilot