[GoGoKo699]

Add a reciprocal Sister project notice immediately below the README title, so the relationship is visible on first opening. The notice names the other repository, links it directly and states the shared benchmark and distinct contribution.

The diff contains only two added lines in README.md, with no deletions. Every previous byte outside that insertion, including all formulas, headings, anchors and detailed relationship sections, is preserved.

Validation:

• Actual live GitHub first-screen inspection confirms both notices directly below their titles, fully visible without scrolling; peer links are correct.
• Fresh 1440/760 captures confirm the notices. Retained article bodies match previously reviewed pixels after explicit alignment; header reflow and a footer border were inspected separately.
• Scientific and hosted head workflows pass: 41385291321, 41385291285.
• Separate merged-main workflows pass: 41385572265, 41385572213.
• The protected 70 files and 317 link checks pass; all 11 tests and 23 scientific groups pass in CI. All 142 retained source files and the source tree match the checked PR revision, with zero report comparison differences in this run.

Merged main: c12f104, exact checked tree 3de156872d80d73cd2a93351f2f93f11057dd7b4.