Repository knowledge base: KNOWLEDGE.md convention and coverage

## Motivation

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## Objective

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## Expected Sub Issue

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JIRA Issue: BA-7304

The issue names a repository-wide KNOWLEDGE.md convention but provides no files, tests, entry points, or concrete subtasks. Start by clarifying the objective, expected coverage, and sub-issues; done criteria are not defined in the current text.

Written by the indexing model from the issue text.