assets(sfx): add sprint-21 interactive object SFX placeholders

docs/audio-assets-sprint19.md

@@ -63,3 +63,19 @@ ffmpeg -i input.wav -c:a libvorbis -q:a 4 output.ogg
 - Prefer the primary pick; use the alt only if the primary is unavailable or unsuitable on preview.
 - Keep music loops between 30–60 s to minimize file size on mobile.
 - SFX should be trimmed with a short (~5 ms) fade-out to avoid clicks.
+
+## Sprint 21 — Interactive Object SFX
+
+All CC0 or CC-BY from freesound.org. Replace placeholder 0-byte files with the downloads below.
+
+| File | Description | Freesound suggestion |
+|---|---|---|
+| `assets/audio/sfx/xray_scan.ogg` | electrical hum / machine beep | search "xray machine beep" or "electrical hum short" |
+| `assets/audio/sfx/tea_pour.ogg` | liquid pouring | search "liquid pour short" or "tea pouring" |
+| `assets/audio/sfx/cradle_rock.ogg` | gentle creak / lullaby chime | search "gentle creak wood" or "lullaby chime" |
+| `assets/audio/sfx/gift_open.ogg` | unwrapping / pop | search "gift unwrap" or "pop sound soft" |
+| `assets/audio/sfx/ambulance_siren.ogg` | short siren sting <1.5s child-friendly | search "toy siren short" or "ambulance beep" |
+| `assets/audio/sfx/delivery_cheer.ogg` | happy chime / fanfare | search "happy chime short" or "fanfare child" |
+| `assets/audio/sfx/object_tap.ogg` | soft tap / click | search "soft tap" or "gentle click" |
+
+All files must be <1.5 s, child-friendly (no harsh/loud sounds), mono or stereo, 44100 Hz, OGG Vorbis.