docs: approve benchmark amendment and sync implementation plans

[dKosarevsky]

Summary

• preserve the approved normative amendment 05e3d7ba86fbaa11a7c9e4072dc1f24039bd7126 and governance successor d6b147aefb0bab0e64a41541a67e2c1b8f4d00ad
• synchronize the five implementation plans with the closed publication-containment, broker-credential, merge-queue, and release-finality protocol
• record plan baseline 9cac807c69e0daf09b2d00c0dc4b5305c91221a8 for implementation

Verification

• uv run ruff format --check .
• uv run ruff check .
• uv run mypy src
• uv run pytest -q — 2749 passed, 2 skipped
• git diff --check

Merge requirement

Use a merge commit so the approved normative and governance successor commit identities remain ancestors of main; do not squash or rebase.