Prefer natural macOS say voices and skip novelty fallbacks

[Copilot]

macOS voice auto-selection currently picks the first en_US voice returned by say -v ?, which can select novelty/system-effect voices and produce unnatural playback. This change makes voice selection deterministic for learning use by preferring a small set of natural English voices and excluding novelty voices from fallback.

• Voice selection

  • Parse the full say -v ? voice list before choosing a voice
  • Prefer a curated set of natural English voices when available:
    • Samantha, Alex, Daniel, Karen, Moira
  • Match on English locales broadly (en_*, en-*) instead of relying on a single exact locale

• Fallback behavior

  • Exclude novelty/effect voices from automatic fallback selection
  • Return no explicit voice when only novelty English voices are available, allowing say to use its default behavior instead of forcing a poor-quality choice

• Regression coverage

  • Add Darwin-specific tests for:
    • preferred-voice selection even when novelty voices appear earlier
    • English fallback that skips novelty voices
    • empty selection when the only English options are novelty voices

for _, preferred := range darwinPreferredVoiceNames {
	for _, voice := range voices {
		if voice.name == preferred && isDarwinEnglishLocale(voice.locale) {
			return voice.name
		}
	}
}

for _, voice := range voices {
	if isDarwinEnglishLocale(voice.locale) && !isDarwinNoveltyVoice(voice.name) {
		return voice.name
	}
}

return ""

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[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

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🟢 Metrics 22 complexity · 6 duplication

Metric	Results
Complexity	22
Duplication	6

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[Copilot]

Pull request overview

This PR improves macOS (say) voice auto-selection to avoid novelty/effect voices and produce more natural, deterministic speech for learning use.

Changes:

• Prefer a curated list of natural English voices (e.g., Samantha/Alex/Daniel/…) after parsing the full say -v ? output.
• Broaden English locale matching to en* locales and update fallback to skip novelty voices (or return empty to let say decide).
• Add Darwin-specific regression tests for preferred selection, novelty-skipping fallback, and “only novelty voices” behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
internal/audio/factory_darwin.go	Implements deterministic preferred-voice selection and novelty-skipping English fallback for macOS say.
internal/audio/factory_darwin_test.go	Adds tests covering preferred voice choice vs earlier novelty voices, fallback skipping novelty voices, and empty selection when only novelty voices exist.

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

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