Add live transcript preview in the recording HUD

While recording, the HUD now shows a rough live transcript using macOS's
on-device dictation model (SpeechAnalyzer + DictationTranscriber), which
also supports Hungarian. It is only a preview: Whisper still produces the
pasted text.

The preview captures the microphone with its own AVAudioEngine, leaving
the AVAudioRecorder path for Whisper untouched, so a preview failure just
means no preview. Audio is buffered from the moment recording starts so
the first words aren't lost while the model spins up; dictionary terms
are passed as contextual strings and replacements are applied to the
preview text. The dictation model for the selected language is
registered/downloaded at launch and on language change, and awaited
inline if needed.

The HUD is wider and shows the last three lines of the transcript; after
recording it stays up as "Transcribing…" until the final text is pasted.
A "Live preview while recording" setting (on by default) turns it off.
No extra permission is required beyond the microphone.

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

macos/Makefile

@@ -11,7 +11,7 @@ BUNDLE_DIR = $(APP_BUNDLE)/Contents
 
 # Compiler settings
 SWIFT = swiftc
-SWIFT_FLAGS = -O -framework Cocoa -framework AVFoundation -framework Carbon -framework CoreGraphics -framework ServiceManagement
+SWIFT_FLAGS = -O -framework Cocoa -framework AVFoundation -framework Speech -framework Carbon -framework CoreGraphics -framework ServiceManagement
 
 .PHONY: all clean build bundle install run dmg