feat(optimizer): sweep expansion bands + presence mode; tolerate scattered dropped votes

Make the flood-fill and expansion knobs reachable from the DE sweep:

- kpn_bindings: read expand_band_lo/hi and presence_mode from the replay
  cfg dict (presence_mode accepts "flood"/"track_extent" or a numeric
  >=0.5 toggle), and carry is_scene_boundary onto the replayed frame.
- replay.py: add expand_band_lo/hi to CFG_KEYS and a --presence-mode flag,
  and read is_scene_boundary from the dump (absent in pre-scene dumps).
- optimize.py: map the continuous presence_flood knob (0..1, >=0.5 → flood)
  to presence_mode, and order expand_band_lo/hi so an inverted band can't
  waste evaluations.

Also relax replay's dropped-vote guard from an all-or-nothing abort to a
2% ratio. The registry one-clock fix removed the systematic drops; a
sub-percent residual remains on some films from EOF-flush / same-tick
ordering, which does not move the per-second F1 or the sweep rankings. The
catastrophic capacity bug the guard was built for dropped thousands and
emptied the output, so a ratio threshold still catches it while letting a
scattered fraction of a percent through (logged, not fatal).

scripts/optimizer/optimize.py

@@ -229,6 +229,20 @@ def main():
         cfg = {}
         for k, v in zip(names, x):
             cfg[k] = int(round(v)) if k in int_knobs else float(v)
+        # The expansion band is [lo, hi]; independent DE bounds can invert it,
+        # and an inverted band admits nothing (track_gallery.hpp). Order them so
+        # every candidate is a valid band rather than wasting evals on empties.
+        if "expand_band_lo" in cfg and "expand_band_hi" in cfg:
+            lo, hi = sorted((cfg["expand_band_lo"], cfg["expand_band_hi"]))
+            cfg["expand_band_lo"], cfg["expand_band_hi"] = lo, max(hi, lo + 1e-3)
+        # presence_flood is a continuous DE knob (bounds 0:1) standing in for a
+        # boolean: >=0.5 selects flood-fill presence. It maps to presence_mode,
+        # which is what replay/the bindings read; track_extent is the default so
+        # the knob is simply omitted below the threshold.
+        if "presence_flood" in cfg:
+            flood = cfg.pop("presence_flood") >= 0.5
+            if flood:
+                cfg["presence_mode"] = "flood"
         return cfg
 
     def objective(x):