## What
Adds a new **`effects`** cosmetic category alongside `skins`/`flags`.
Each effect is discriminated by **`effectType`** (only
`transportShipTrail` today), whose visual config lives in
**`attributes`** (`solid` / `rainbow` / `pulse` / `gradient`). Schema
matches the production cosmetics.json shape exactly (incl. the `url`
field).
**This PR is UI + taxonomy only — the in-game WebGL trail rendering is
intentionally deferred.**
## UI
- **Store** gains an **"Effects"** tab.
- **Home page** gains an **"Effects"** button opening a picker modal.
- Both render effects **grouped by `effectType` with a sub-header per
type**, via a shared `<effects-grid>` Lit element (`mode="select"` for
the picker, `mode="purchase"` for the store). The picker shows owned
effects + a Default tile and persists per-type; the store shows
purchasable effects.
## Data flow
- Ownership via `effect:*` / `effect:<name>` flares (reuses
`cosmeticRelationship`).
- Selection is a per-`effectType` map persisted in UserSettings
(`settings.effects`).
- Server validates in `isEffectAllowed`, wired into `isAllowed`.
- `getPlayerCosmeticsRefs` / `getPlayerCosmetics` resolve effects the
same way as skins/flags (kept-on-fetch-failure, server is authority).
## Tests
- `tsc --noEmit`, ESLint, Prettier clean; full suite green.
- New: `CosmeticSchemas` parse tests (incl. parsing the **real**
`read_transport_trail` entry), `UserSettings` per-type selection, and
`Privilege` effect validation.
## Notes / follow-ups
- The effect's display label shows **"Boat Trail"** for the
`transportShipTrail` type (friendlier than the id).
- Closed-source API gap: `/shop/purchase` (`purchaseWithCurrency`) needs
to learn `"effect"` for **currency** purchase of effects; the
**dollar/product** purchase path already works. Client types were
widened accordingly.
- In-game wake rendering can be ported from #4416.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Evan