fix(normalizer): expand wh-word 're contractions espeak voices as -ray

[radzrader]

AI assisted (Opus 4.8) but tested in my own running version on my GB10 Spark.

Description

The bug

espeak's letter-to-sound gives some 're contractions a spurious stressed
/ɹeɪ/ ("-ray") ending. The clearest example is "how're", which is
phonemized as hˌWɹˌA = /haʊ ɹ eɪ/ — "how-ray", which listeners hear as
"harry". The trailing A is the same /eɪ/ vowel as "day" (dˈA), so the
contraction gets an incorrect diphthong that isn't in the intended word.

This is not voice-specific - it reproduces in both the American (a) and
British (b) pipelines, because it happens in g2p, upstream of the model.

Phonemes (via /dev/phonemize), contracted vs. expanded:

input	phonemes	reads as
how're you	hˌWɹˌA juː	"how-ray"
how are you	hˌW ɑː juː	"how-ah" ✓

The fix

Expand the affected contractions to their two-word form in normalize_text
before phonemization. This sits alongside the normalizer's existing always-on
English fixups (Dr.→"Doctor", yeah→"ye'a", etc.).

The list is deliberately limited to the contractions that actually break -
the wh-words plus there/these/those. Common contractions that already
phonemize correctly are intentionally left untouched, so this changes nothing
for them:

contraction	phonemes	verdict
you're	jɔː	correct - left alone
we're	wɪə	correct - left alone
they're	ðɛː	correct - left alone
how're	hˌWɹˌA	broken → how are
what're	wˌɒtɹˌA	broken → what are
where're	wˌɛːɹˌA	broken → where are
who're	hˌuːɹˌA	broken → who are
when're	wˌɛnɹˌA	broken → when are
why're	wˌIɹˌA	broken → why are
there're	ðɛːɹˌA	broken → there are
these're	ðiːzɹˌA	broken → these are
those're	ðQzɹˌA	broken → those are

The regex is case-insensitive and preserves the leading word's capitalization
(How're → How are), and matches both the straight (') and typographic
(’) apostrophe.

Audio (before / after)

Same sentence, bf_emma, listen to "how're":

• 01_before_nofix.mp3 — this codebase, normalization off (bug) → "harry"
• 02_after_fixed.mp3 — this codebase, with this fix → "how are"
• 03_ab_combined_before_then_after.mp3 — both back-to-back

01_before_nofix.mp3
02_after_fixed.mp3
03_ab_combined_before_then_after.mp3