tests: a guard that actually regresses on the resync storm

The split resync loop (f898350) had no test. Two attempts at one were worthless
and are not in this commit: a scroll-based guard passed with the bug
reintroduced, and a constructed anchor -- inside the loaded function, outside
its mapped span -- skipped, because on this target the map covers the whole
function. The real trigger is the race window while the decomp map lags the
decompiler re-pointing, which is tedious to force but wide open in split_view's
own flow.

So split_view counts lookup_funcs across its body and bounds it. Verified both
ways, which is the only reason it's worth having: 29,227 calls with the bug put
back, under 500 with the fix. The bound is loose because the bug was three
orders of magnitude out, not a near miss.

733 checks, 139s.

0 files changed, 0 insertions, 0 deletions