[codex] Add Parakeet word boosting

[HashiamKadhim]

Summary

• adds a Parakeet boosted-words editor in Model settings and persists the custom vocabulary
• loads the vocabulary through FluidAudio custom vocabulary support when the Parakeet engine initializes
• persists FluidAudio rescorer fixes so longer matching spans win over shorter overlapping spans and short clips do not crash when multi-word aliases are configured
• removes the nested scroll view that was squishing the Parakeet model picker

Validation

• git diff --check
• xcodebuild test -scheme OpenSuperWhisper -configuration Debug -derivedDataPath build -destination 'platform=macOS,arch=arm64' -skipPackagePluginValidation -skipMacroValidation -UseModernBuildSystem=YES -clonedSourcePackagesDirPath SourcePackages -only-testing:OpenSuperWhisperTests/AppPreferencesParakeetVocabularyTests CODE_SIGNING_ALLOWED=NO CODE_SIGN_IDENTITY="" CODE_SIGNING_REQUIRED=NO
• ./run.sh build
• signed and verified the debug app with codesign --verify --deep --strict
• saved-audio probe with a generic boosted entry like customterm: spoken alias: base transcript matched the spoken alias, boosted transcript emitted customterm
• short one-word saved-audio probe with multi-word boosted aliases configured returned normally instead of crashing