Refresh matched DTLZ2 Wilcoxon and land the 0.2 surface

[jkbennitt]

Summary

Checks off the remaining near-term 0.2 items except nuget.org: a matched 15-seed Wilcoxon refresh, net8.0+net10.0 multi-targeting, GD+, and a DocFX API build. Package version stays 0.2.0; the work is listed under Unreleased. GitHub Packages publish is unchanged and still the only registry.

Wilcoxon (measured)

python tools/oracle/run_multiseed_wilcoxon.py --problems zdt1 dtlz2 --seeds 15 with pymoo 0.6.2. DTLZ2 uses n_var=12 on C# (Dtlz2Problem(k: 10)) and pymoo. ZDT2 is still not a Wilcoxon table (quality bar remains gens=250 + PymooCompatible).

• ZDT1 reproduced the previous cells: median 0.053173 vs 0.0695884, Mann–Whitney U = 65, p = 0.0512394. The pymoo column is still res.F.
• DTLZ2 replaces the old n_var=10 pymoo column. Median 0.00451168 vs 0.00388327 (ratio 1.16183). Mann–Whitney U = 168, p = 0.0225311. Wilcoxon signed-rank W = 15, p = 0.0114901. Better median is pymoo. Seed 1 is 0.00403168 / 0.00308392, the same matched pair already in docs/ORACLE-RESULTS.md.

Other surface

• Library, tests, and BasicUsage target net8.0 and net10.0. tools/OracleCompare stays net10.0. CI and the GitHub Packages workflow install both SDKs.
• PerformanceIndicators.GenerationalDistancePlus is Ishibuchi GD+ (mean modified distance). Tests are hand cases, including a point that weakly dominates the reference (GD+ = 0, Euclidean GD = √2).
• dotnet tool restore && dotnet docfx docfx.json builds _site/. CI job api-docs runs that command. Generated api/ and _site/ stay gitignored.

Checklist

• dotnet test Unsga3.slnx -c Release passes locally (110 tests on net8.0 and 110 on net10.0)
• CHANGELOG.md updated under Unreleased (if user-visible)
• Public API changes documented (XML docs / README)
• If survival / normalization / metrics changed: noted oracle impact (or re-ran multi-seed)

Test plan

• dotnet test Unsga3.slnx -c Release on net8.0 and net10.0
• dotnet run --project samples/BasicUsage -c Release -f net8.0 and -f net10.0 (same seed, same front)
• dotnet tool restore && dotnet docfx docfx.json (0 warnings; nupkg contains lib/net8.0 and lib/net10.0)
• 15-seed Wilcoxon harness (zdt1, dtlz2, n_var=12)