#26: fix to_gpt regex to strip space before punctuation

[VasilevNStas]

Problem:
The regex alternation (\\?|!|\\|,|:) in to_gpt() uses \\|, which matches the two-character sequence |,, not a bare comma. Space before a comma is never removed.

Solution:
Replace alternation with character class ([?!,:]). This correctly strips a space before any of ?, !, ,, :. Added regression test removes spaces before punctuation.

Checklist:

• npx eslint . — 0 errors
• npx jest --coverage — all pass, coverage >=90%
• npx tsc --target es2020 --module nodenext --outDir dist — 0 errors
• make — lint + test + it + tsc pass

[VasilevNStas]

@yegor256 @edmoffo please review

[kreinba]

Character class [?!,:] replaces the alternation that contained an erroneous escaped pipe before the comma, so a space before any of the four punctuation marks is now stripped. Regression test exercises all four marks, jest and eslint pass locally. Resolves #26. 0 inline comments.

[VasilevNStas]

@yegor256 @edmoffo please re-review