format_units zfill off-by-one for amounts equal to 10^decimals

Opus finding

format_units zfill off-by-one for amounts equal to 10^decimals

• symbiosis/scripts/symbiosis-quote.py:26-30

The logic mostly works but: for `amount_raw='0'` with decimals=6, s='0000000' (7 chars), int_part='0', frac_part='' -> returns '0' (ok). For very large amounts, `float()`-free formatting is good. However, when `amount_raw` is non-digit (e.g., '' default), `'0'.zfill(7)` is fine but `int(integer+frac)` in to_smallest_units would already have rejected it. Lower-severity concern: if amount_raw contains a leading '+' or scientific notation (the API generally returns canonical strings, so this is unlikely), parsing breaks. Severity low because Symbiosis returns canonical integer strings.