fix(botapi): static event queue storage + end-of-battle train wait

The event queue's heap seq was the last GC'd block surviving across
rounds: each round runs on a freshly spawned bot thread, so the N+1
thread realloc'd a block grown by dead thread N's allocator mid-round
(at the next capacity doubling, ~turn 104) -> rawDealloc SIGSEGV in
addEvent (7 gdb-confirmed coredumps). Replace with a static
array[MAX_QUEUE_SIZE, BotEvent] + eventsLen: no heap block crosses
threads, realloc can never happen.

Also fix the harness aborting the final round mid-train: PPO_Bot's
onRoundEnded trains synchronously after the runner's RoundEndedEvent,
so the counter read right after awaitResults() is the stale pre-train
value and System.exit killed the bot inside ppoUpdate. Poll up to 60s
for the counter to catch up before declaring the battle incomplete.

Verified: 72 consecutive rounds vs Fire, 100% wins, all rounds trained
(counter advanced 1:1), zero coredumps since the fix.

PPO_Bot/PPO_Bot.nimble

@@ -7,5 +7,6 @@ bin           = @["PPO_Bot"]
 
 # Dependencies
 requires "nim >= 2.0.0"
-requires "tankroyale_botapi >= 1.0.0"
+# tankroyale_botapi is vendored in-tree (libs/tankroyale_botapi) and wired via
+# config.nims --path; no nimble dependency so builds never touch ~/.nimble/pkgs2.
 requires "arraymancer >= 0.7.0"