docs+tools: the per-entity OB flag is refuted, and the counter decrements when the player kills

With the pilot finally shooting, the experiment completed both halves. Sample A
at counter 12 over 120 entities gave 2 offsets where exactly 12 entities share a
value; the counter then went 12 -> 11 and NEITHER survived. So within +-0x400 of
an entity's position triple there is no 4-byte word whose shared-value population
tracks REMAINING OB.

The limits are recorded as part of the result, because they bound it: the test
asks which entities share an EXACT 32-bit value, so a single bit ORed into a word
that also carries health or a timer would never show up - a bit-level version of
the same differential is the follow-on. Anything outside the window, or on
entities that entities2 cannot see (it types by position CHANGING, so stationary
objectives are invisible), is untested too, and the populations differed a lot
between samples - 120 against 194.

Separately: REMAINING OB went 12 -> 11, the first decrement of this whole
investigation, while pilot.py logged 411 fire=1 samples and the HUD reached YOU
KILLED WARPLANES 0003. Stated carefully - it does NOT show the counter counts
kills, since an earlier run had the hostile population fall by a third with no
movement; it shows some kills close something the counter tracks.

Two robustness fixes: ob_flag retries an empty entity sample (one void run was
caused by exactly that), and Pad releases everything on interpreter exit - a
file-backed pad PERSISTS after its writer dies, so a tool killed mid-press would
leave a button held and the game would walk through menus on its own.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PMRJjbxLqZtsb5Vb7KunPE

docs/re/captures/ob-flag-refuted-stage02.json

@@ -0,0 +1,11 @@
+{
+ "nA": 12,
+ "nB": 11,
+ "hud_a": 12,
+ "hud_b": null,
+ "entities_a": 120,
+ "entities_b": 194,
+ "class_matches": [],
+ "candidates_a": 2,
+ "survivors": []
+}