docs: align contributor guidance and architecture with current behavior

[kevintseng]

Summary

• Align the Node minimum, isolated test command, maintained README locales, and version anchors with the current repository.
• Correct recall/forget flows, generated path sharing, native delivery wording, session citation accounting, and documentation links.
• Describe the doc-claims checker as a bounded check, not proof of every documentation statement.

Validation

• node scripts/check-doc-claims.mjs (exit 0)
• node scripts/check-codemap-parity.mjs (exit 0)
• node scripts/check-version-coherence.mjs (exit 0)
• git diff --check (exit 0)
• All five changed documents were independently checked against source, including a simplification review.

Documentation only. No product behavior, version, or release changes; full product tests were not rerun.