llm_directed: directed sex (breed offspring + select on verifier) — E10 in real weights

Adds the "directed sex" operator (E10) the moe regime-flip pointed to: don't
commit to one a-priori blend — breed a population of recombinant offspring
(specialists merged at Dirichlet-sampled weights), score each on a held-out
validation split with the verifier, and keep the fittest, reported on a fresh
test split. Two breeding objectives: best-overall and best-worst-family.
src/llm/directed.py + kind llm_directed, reusing the cached specialists.

Result — refinements pay off in proportion to how far the uniform soup is from
optimal:
- 0.5B (soup dilutes): directed selection beats soup on the bred objective —
  directed_overall 0.69 > soup 0.64; directed_balanced worst-family 0.37 > 0.26.
  Riders: single-objective selection trades off the other axis (overall-breed
  tanks lists to 0.17); a global blend still trails per-input routing (0.74).
- 7B (Imperial CX3, soup already composes to ceiling on near-saturated families,
  strings/arith 1.00): directed ~= soup (0.868 ~ 0.873, marginally below via a
  val/test overfit gap) — no fitter offspring to breed.

Through-line across all four LLM runs: "merge, don't average" and its refinements
(routing, directed selection) are weak-base / suboptimal-default phenomena — they
help at 0.5B and are inert at 7B. Honest limitation kept in the writeup: the 7B
families are near-saturated, which caps the headroom; a harder unsaturated
benchmark is the fair next test.

Also folds in the two llm_moe local manifest/config files missed in 8da0dac.
+3 directed unit tests (130 green). Results in results/llm_directed{,_hpc}/
(parquet gitignored).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tasks/todo.md

@@ -367,3 +367,16 @@ C3 vertical claim deferred.*
   spec 0.57). So "merge, don't average" is a **weak-base law**, not universal — union wins under
   dilution (0.5B), fusion wins under composition (7B). Refines E8. Next: fusion + offspring-selection
   (directed sex). `results/llm_moe_hpc/` README + regime-aware figure.
+
+**2026-07-05 — Directed sex (`llm_directed`): E10 in weights = breed offspring + select on verifier.**
+- `src/llm/directed.py`: sample a population of Dirichlet-weighted merges, score on a held-out VAL
+  split, keep the best-overall + best-worst-family, report on a fresh TEST split. `kind: llm_directed`.
+- **0.5B:** directed selection beats the single a-priori soup on the bred objective — directed_overall
+  0.69 > soup 0.64; directed_balanced worst-family 0.37 > soup 0.26. Riders: single-objective selection
+  trades off the other axis (overall-breed tanks lists 0.17); a global blend still trails per-input
+  routing (0.74). **7B (CX3 L40S, 9 min):** directed ≈ soup (0.868 ≈ 0.873) — soup already composes to
+  ceiling on near-saturated families (strings/arith 1.00), no fitter offspring to breed.
+- **Through-line:** recombination refinements pay off ∝ how suboptimal the default soup is — big at
+  0.5B, nil at 7B. Honest limit: 7B families near-saturated; a harder benchmark is the fair next test.
+- `configs/llm/{directed,directed_hpc}.yaml`, `figures/plot_llm_directed.py`, READMEs, `hpc/llm_directed.pbs`,
+  Makefile `llm` target, +3 tests (130 green). `results/llm_directed{,_hpc}/`.