Introduces a new "bonus item" system alongside the existing smashables:
- **Gameplay**: Floating collectible prizes (CTC box, guitar, cash) that the bus passes through with zero physical response. On first contact, the item pops (scale-up + fade) and spawns a radial burst of tinted firework particles that arc down under gravity, settle on terrain, and fade out. Each collected item scores 100 points on the end-of-level tally.
- **Config**: `BONUS_ITEM` in `config.js` holds all tuning knobs (particle count, speed range, spin, lifetime, per-type tint palette, pop scale/duration). `SCORE.perBonusItem` added.
- **Entity**: New `BonusItemManager` class owns static sensor bodies for each bonus item, detects bus collisions, and orchestrates the pop + firework burst animation. Particles are real Matter bodies exempted from bus/kid collision so they can land on terrain without affecting gameplay.
- **Editor**: "Smashables" section renamed to "Placeables" with a kind toggle (Smashables vs Bonus items). Bonus items are float-only with no gravity option. Preview map, click-to-place, item list, and export all support both kinds. `splitPlaceables()` in `levelBuilder.js` splits the unified editor list into the two level arrays (`items` / `bonusItems`).
- **Levels**: Levels 2–6 updated with bonus item placements (and some additional smashable items).
- **Assets**: New `bonus-items.png` spritesheet (9 frames: 3 bonus items × [item + 2 firework objects]) registered in the asset manifest.
- **Score screen**: `_revealBonus()` method in `LevelScoreScene` displays collected bonus count and points, skipped when zero.
- IntroScene: use bg_main.png poster art as full background, layer
logo.png with a breathing tween aligned to the baked wordmark via
fitted similarity transform constants, and add a double-stroke
"Press any key" prompt (replaced auto-advance with input-only trigger).
- MainMenuScene: replace text title with bg_menu.png background and
centered logo.png overlay; add semi-transparent background pill to
instructions text for readability over the treeline.
- LevelSelectScene: add bg_menu.png background and background pill to
back button text for contrast.
- assetManifest: register bg_main, logo, and bg_menu textures.
- New assets: bg_menu.png, ctc.png, paid.png, bg_main.png, logo.png.
Brian Fertig