Fix last SKIP control flow in scalar context

[fglock]

Fixes control flow propagation for last SKIP through function calls in scalar context.

Problem

Test #2 in skip_control_flow.t was failing:

sub inner2 { last SKIP }
sub outer2 { my $x = inner2(); return $x; }
SKIP: { my $r = outer2(); }

The last SKIP in inner2() wasn't exiting the SKIP block because the control flow marker wasn't being checked after outer2() returned.

Solution

Added registry check in EmitBlock.java after each statement in simple labeled blocks (≤3 statements without loop constructs). The check:

• Calls RuntimeControlFlowRegistry.hasMarker()
• If marker present, calls checkLoopAndGetAction(labelName)
• Jumps to nextLabel if action != 0

Limited to simple blocks to avoid ASM VerifyError in complex code.

Results

• ✅ skip_control_flow.t: all 3 tests pass
• ✅ make: passes with no regressions
• ✅ No ASM errors