fix(plot): no-floor route2 deploy panel was blank -- hk_abl column present but all-nan

The plotter picked hk_abl (dense proxy) whenever the COLUMN existed, but no-floor
runs (rollout_ablate_frac=0) emit hk_abl as 0/0 -> all-nan, so the deploy panel
came up empty. Test for finite data (_has_data) not column presence; fall back to
the sparse-but-real hk_dep (every eval_ablate_every steps). _ema carries values
across the nan gaps -> a held step-line.

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

docs/figs/dyn_sub4.png

@@ -0,0 +1 @@
+../../out/figs/dyn_sub4.png

docs/figs/dyn_sub4_hack_overlay.png

@@ -0,0 +1 @@
+../../out/figs/dyn_sub4_hack_overlay.png