feat: Irish help page with comprehensive pronunciation guide

1300+ line help file covering all three dialects (Connacht, Munster,
Ulster) with full IPA symbol tables, broad/slender distinction guide,
lenition/eclipsis mutation tables, stress patterns, vowel digraphs,
sonorant system, epenthesis rules, and dialect-specific feature docs.
Based on the engine's 17-pass rule pipeline code.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: hellpanderrr