fix: don't re-invert a shared 'if' condition in a duplicated block

[obus-globus]

NOTE: This is what one may call "AI slop". Feel free to close this PR if it's not up to your quality standards or even if you just aren't interested in reviewing it. I use these changes downstream on an APK and thought I might as well make a PR offering to upstream them, as your CONTRIBUTING.md doesn't say anything discouraging this.

Description

Demonstrated on the java/class input path. A condition that heads a block belonging to more than one region is inverted one extra time, flipping its first operand. For

static int test(boolean a, boolean b, boolean x, boolean y) {
    int r = 2;
    if (a || b) {
        r = (x || y) ? 1 : 0;
    }
    return r;
}

the inner (x || y) decompiled as (!x || y): the first operand picked up a spurious negation.

IfRegionMaker.process inverts a simple condition in place: IfInfo.invert (via IfCondition.invert) calls Compare.invert, which mutates the block's shared IfNode in place. The (x || y) block heads a merged short-circuit condition and is also reached from two predecessors (AFlag.DUPLICATED), so it is processed as a region head more than once. The DONT_INVERT guard that prevents a second in-place inversion was only set on the simple-invert path, not when the condition was built by mergeNestedIfNodes, so the later standalone pass inverted the already-built condition again and flipped its first operand.

Set AFlag.DONT_INVERT after both the merge and the simple-invert branches, so a shared block's condition is inverted at most once regardless of how it was built.

Includes an integration test.