Fix Fillomino [?] region size validation (fixes #462)

[mashinosatoshi]

Description

This PR fixes issue #462, where two ? regions of the same size touching each other incorrectly passed the answer check without raising a bsSameNum error in Fillomino.

Root cause

When a region is composed entirely of ? markers, its logical number in the graph was evaluated as -2. During the adjacent area matching (checkSideAreaNumberSize), values <= 0 are skipped to avoid false flags. As a result, identical-size ? regions did not trigger the validation for "same size area sharing an edge".

Fix details

Updated the graph generation logic so that it assigns the current area size (clist.length) as the region's number when it consists exclusively of ?. This makes its behavior consistent with empty cell regions, ensuring the adjacent size comparison works correctly and errors are properly flagged.

A test case proving this validation fix has been added in test/variety/fillomino_test.js.

Fixes #462

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[x-sheep]

Thanks for the pull request. While question marks should generally be avoided completely in finished puzzles, there's no harm in fixing the issue of course.

[mashinosatoshi]

Thank you for your review.
Please check changes.

[x-sheep]

Thanks!