Java runtime accepts non-ASCII digits as numbers (Arabic-Indic, Devanagari, full-width) where COBOL NUMERIC/NUMVAL would not #3831

What: Probe: Character.isDigit('١') is true; new BigInteger("١٢") gives 12, as does full-width １２; Integer.parseInt("१२") gives 12. CobolRecords.zoned / decimal() (repository_forge.py:179,256) therefore accept data the mainframe would reject. And decimal("1,5") throws even in a decimal-comma program.

Test: A screen input of ١٢٣ or １２３ in a numeric field. Expected: COBOL's invalid-data path.

Fix: Validate [0-9] explicitly; add a NUMVAL helper that honours DECIMAL-POINT.

Found by a cultural-assumptions audit (2026-09-26): confirmed in code or by probe (JDK 17 locales, IBM code-page decoding, the harness's GnuCOBOL image) unless marked plausible.

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