fix: use STRUT vowel (ʌ) instead of schwa (ə) in stressed syllables

[yocontra]

Summary

The ipa-dict source data uses ə (schwa) for the STRUT vowel in words like "but", "cut", "run", "come", "love", "other", "mother", "nothing", etc. In standard IPA for English, the STRUT vowel is /ʌ/ — a distinct phoneme from schwa /ə/.

These are different vowels:

• ə (schwa) — unstressed, reduced vowel: "the" = /ðə/, "about" = /əˈbaʊt/
• ʌ (STRUT) — stressed, open-mid back vowel: "but" = /bʌt/, "cut" = /kʌt/, "love" = /lʌv/

The ARPABET mapping in src/consts.ts correctly maps AH → ʌ, but the ipa-dict source data uses ə where ʌ is expected, causing hundreds of common words to have incorrect transcriptions.

What this PR does

Adds a fixStrutVowel() post-processing step to scripts/build-dict.ts that runs after merging dictionaries but before trimming. It detects ə in stressed closed syllables and converts it to ʌ.

The regex logic:

• Finds ə that is the first vowel after a stress mark (ˈ or ˌ), meaning it's in a stressed position
• Requires ə to be followed by a consonant (closed syllable), which distinguishes STRUT from genuine schwa
• Open syllable ə (like "the" = ðə) is correctly preserved

Examples of fixes

Word	Before (incorrect)	After (correct)
but	ˈbət	ˈbʌt
cut	ˈkət	ˈkʌt
come	ˈkəm	ˈkʌm
love	ˈɫəv	ˈɫʌv
other	ˈəðɝ	ˈʌðɝ
mother	ˈməðɝ	ˈmʌðɝ
nothing	ˈnəθɪŋ	ˈnʌθɪŋ

What is preserved (no false positives)

Word	IPA	Reason
the	ðə	No stress mark — not touched
about	əˈbaʊt	Initial ə is unstressed — not touched
sofa	ˈsoʊfə	Final ə is not the first vowel after stress — not touched