v0.12.1-beta.1 — isolate the GP Bikes reload crash

Diagnostic build. Not for general use. This is a pre-release, so frostmod.exe --update and the MXB App will both ignore it — everyone stays on v0.12.0 unless they download this by hand.

What it's for

The v0.12.0 logs pinned GP Bikes' reload crash to step 1 — tracks — three times out of three, with no step 2 ever reached. That tells us which loader dies, but not why. Two explanations are still standing:

1. That one loader is unsafe to re-run.
2. Replaying any loader from where we replay it is unsafe.

This build separates them with one flag.

How to run it

frostmod.exe --game gpb --unsafe-reload-from=2

That skips the tracks step and starts at step 2. Then reload mods in game, as before.

• If it completes — you'll see [reload] done - steps 2..13 completed — the tracks loader alone is the problem, and the fix is targeted.
• If it dies at step 2 the same way, the problem is where we replay from, not what we replay.

Either result is decisive. Send frostmod.log from next to frostmod.exe.

--unsafe-reload-from implies --unsafe-reload, so you don't need both. Plain --unsafe-reload still runs the whole table exactly as it did.

Also in this build

The reload's thread-id line no longer presents the two thread ids as an open question. Your logs answered it: the boot scan and the reload run on the same thread in every session, so the race we suspected isn't happening. That theory is retired, and the notes now record what replaced it.

Nothing else changed. MX Bikes is untouched.