Cross-provider positions + USD value for an arbitrary wallet

One call fans out to every supported provider for `user`. Polymarket returns the position array + total USDC value; Hyperliquid returns `clearinghouseState` (perp positions, margin) as `native`, with `valueUsd` = the COMPLETE account value (perp across every dex + spot + vault + staking — same source as `/v1/me/stats`) broken down in `buckets`. HL valuation is mode-aware (`accountMode` echoes `userAbstraction`): unified accounts hold perp margin on the spot balance, so the perp bucket is unrealized PnL only — no double counting. `summary.totalValueUsd` sums providers that exposed a number — providers that didn't (or upstream failed) appear in `warnings`. Pass `?provider=polymarket,hyperliquid` to fan out only to specific providers; omit for all.