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/config.nims

@@ -6,3 +6,8 @@ switch("threads", "on")
 when withDir(thisDir(), system.fileExists("nimble.paths")):
   include "nimble.paths"
 # end Nimble config
+# Use the repo-vendored Tank Royale bot API (libs/) instead of the nimble pkg.
+# The pkg copy lived in ~/.nimble/pkgs2 and was patched ad-hoc; vendoring makes
+# the build self-contained and keeps the cross-thread Channel fix in-tree.
+# Must come AFTER the nimble.paths include: later --path wins the import search.
+switch("path", thisDir() & "/../libs/tankroyale_botapi")