docs(v0.7.29): clarify query explanations and answer hierarchy

[qiansc]

Summary

• Complete 0.7.29 query guidance with direct conditional answers, mechanism explanations and claim-local evidence.
• Adapt section hierarchy to question complexity without a fixed answer template.
• Earlier repository recovery and document investigation changes are already merged in feat(v0.7.29): guide document code investigation and repository recovery #43.

Verification

• Plugin generation and focused source/projection checks previously passed.
• Tests are not rerun for this fast release, as explicitly requested by the maintainer.
• Release uses the existing skip-checks option; builds, package audits and publication checks remain enabled.