feat: real pre-recording Scene Inspector panel

[Alfredoalv13]

Summary

• Replaces the Studio window's static, fully-disabled "Scene Inspector" rows (Format/Canvas Style/Pointer/Captions — hardcoded text with zero state or handlers) with real controls.
• Format -> default aspect ratio, Wallpaper -> default background, Pointer -> default cursor style, Caption Language -> default transcription language — all wired to the same persisted EditorPreferences the post-recording editor already reads on load.
• Adds autoCaptionLanguage to EditorPreferences (new field, defaults to "auto").
• Deliberately does NOT auto-trigger caption generation on fresh recordings — that would mean silently kicking off a Whisper transcription (which can take a while and needs a downloaded model) without the user asking. The language preference just applies whenever they do click "Generate Captions" later.

Test plan

• npx tsc -p tsconfig.json --noEmit — clean
• npx vitest --run — 819/819 passing
• Built, signed, and ran the packaged app directly
• Confirmed the Studio panel renders real current values (not placeholder text) for all four rows
• Changed the Pointer setting to "Dot" in the Studio panel, confirmed via getAppSetting that it persisted
• Opened a fresh editor window and confirmed both the persisted value and the actual cursor-style selector in the editor's Settings panel reflected "Dot" as selected