Route tleCatalogNumber() and noradIdFromSatnum() through one decoder that
accepts only plain digits or a valid Alpha-5 field. parseInt and Number()
read '2554A', '255 4', '-1234', '0x1F0', '1.5' and blank as numbers; they
now return null/NaN. Digit satnums of any length still decode, so OMM
satrecs numbered past 99999 keep working.
Add a layer test that several Alpha-5 satellites survive ingestion dedupe,
the changelog fragment for #767, and note in CURRENT-STATE that this is
Alpha-5 TLE compatibility and malformed fields are rejected.