wc-population-diversity — anti-inbreeding & selection-pressure governor

Implements the diversity-maintenance and selection-pressure ideas the Evolution document is explicit about: "plant breeders care about preserving genetic diversity; agent researchers care about maintaining behavioural diversity — same problem," and "selection pressure too high → population collapses; too low → progress is slow," and "repeatedly refining the same strategy leads to local optima" (inbreeding). In this system, diversity isn't an aesthetic — it's what guarantees the manager sees a genuine choice (a cover path and a climb path), not six shades of the same template.

Inputs

• The offspring set (post-recombination, post-mutation), each with squad/plan, ownership profile, and variance_band.
• The objective θ/k and the elite-set history (was selection already monochrome upstream?).

Workflow

- [ ] 1. Measure collapse metrics across the offspring set
- [ ] 2. Compare against diversity floors
- [ ] 3. If collapsed: inject an under-represented genotype and/or raise mutation; signal re-run of crossover+mutation
- [ ] 4. Tune selection pressure (widen/tighten the elite set)
- [ ] 5. Emit the diversity report

Step 1: Collapse metrics