docs: refresh blog+README for route2/deploy-eval; embed key dynamics plot; drop sparse-only dots

- blog: mark as erase-n=2 draft, note route2/exploration-floor/deploy-eval are the
  current direction; embed dyn_sub4_hack_overlay.png (force-added); ASCII em-dashes;
  de-bold the arm list (#15 tell)
- README: add route2 arm + apples-to-apples deploy-eval to 'What we compare'; stale
  banner on the n=1 mix=0.5 findings
- plot_dynamics: remove _mark_if_sparse (asymmetric sparse-only dots); EMA-held line
  for all arms
- train.py: fix 'held-out greedy' -> 'held-out eval subset, T=0.7' (deploy eval is
  sampled, not greedy)

Co-Authored-By: Claudypoo <288921227+claudypoo@users.noreply.github.com>

src/projected_grpo/train.py

@@ -419,7 +419,7 @@ class StepLogger:
         if arm in ("routing", "routing2"):
             cols += [
                 _Col("q_egy", 6, "qE", ".2f", "grad energy into quarantine ‖g_quar‖/(‖g_keep‖+‖g_quar‖); ~0.5+ rising = learning dumped into the thrown-away knob"),
-                _Col("hack_deploy",  7, "hk_dep",  "+.2f", "DEPLOY-eval hack (quarantine deleted = deployed model); held-out greedy, eval_ablate_every steps; the plot number"),
+                _Col("hack_deploy",  7, "hk_dep",  "+.2f", "DEPLOY-eval hack (quarantine deleted = deployed model); held-out eval subset, T=0.7, every eval_ablate_every steps; the plot number"),
                 _Col("solve_deploy", 7, "slv_dep", "+.2f", "DEPLOY-eval solve"),
                 _Col("hack_abl",  6, "hk_abl",  "frac", "FREE per-step deploy proxy: hack rate on the ablated (deploy-mode) rollout slice; train prompts, noisier than hk_dep"),
                 _Col("solve_abl", 6, "slv_abl", "frac", "free per-step deploy proxy: solve rate on the ablated rollout slice"),