wc-building-block-crossover — recombine modules, then repair

Implements the recombination step of evolution-protocol.md against the module map in building-blocks.md. The discipline that defines this skill, straight from the Evolution document: a squad is not a flat list of independent slots; it is modules with internal linkage, and crossover must operate at module boundaries or it destroys the very things that make the parents good. "Excellent planning + Excellent memory without rediscovering both independently" — here: the best captain core and the best clean-sheet stack, fused.

Inputs

• The elite candidate set (from fitness selection), each with its block tags and per-block quality.
• Live constraints from tournament-state.md: budget (group $100m / KO $105m), nation cap (3 group, current-phase cap KO), phase.

Workflow

- [ ] 1. For each block slot, rank the elites by that block's quality (per-block fitness contribution)
- [ ] 2. Compose offspring by harvesting the top block from different parents (try a few combinations)
- [ ] 3. REPAIR each offspring to feasibility — cheapest block first, never gut a value block
- [ ] 4. Drop any offspring whose parents' blocks are fundamentally incompatible (repair would break a block)
- [ ] 5. Record block lineage per offspring; emit the feasible offspring

Step 1–2: Cross at block boundaries