Bug in .bent file parsing

[jan-stevens]

Molecule names of the form <integer>M<suffix> (e.g. 10MG) are incorrectly parsed as a concentration value rather than a molecule name.

Error

Error: found 'concentration (10M)' expected ',', 'word "satisfies"', ...
     ╭─[ cytosol.bent:405:1 ]
     │
 405 │ 10MG  0.000064M   from "structures/metabolites/10MG.gro"     in cytosol
     │ ─┬─  
     │  ╰─── concentration (10M)

10MG should be parsed as a molecule name, not as the concentration 10M. The parser matches <integer>M as a concentration before attempting to match a molecule name, which breaks the .bent input file. This is a common naming convention in metabolite databases (e.g. 10MG for 10-methylguanine).