[NaNIsaac]

Keep docs/index.md as the overview source and generate the marked README block from it. Editing the source now has one explicit sync command, and the shared README workflow checks the generated result.

• Add --sync-overview <repo-name-or-path> and --check-overview to conventions.py. Preserve code examples and rebase Markdown, reference, image and HTML link destinations for the README.
• Require one block below the introduction, with a full-documentation hub link. Refuse ambiguous or misplaced markers without overwriting the README.
• Enforce drift for QoraGeom and QoraPhase first; warn elsewhere and skip repositories without docs/. Existing documentation quality checks keep their rollout.
• Document the source and sync command in CONVENTIONS.md. Pilot README updates follow separately.

Validation: 11 unit tests passed, conventions and local-CI selftests passed, README runner selftests passed, Ruff check/format and actionlint passed. Local CI ran on Windows; the other OS matrix was not run locally.

local-ci: 4182ce5 | ruff ok | pytest n/a | readme n/a | selftest ok | uv ok | not run: selftest (1 matrix combinations, from [windows-latest] to [windows-latest]) | CI environment differs: selftest, ruff run on ubuntu-latest in CI, windows here