Get trader context (JSON)

Returns a single structured context object for one trader: the full trader profile (same shape as GET /api/v1/trader/{address}) plus a position_summary (sync coverage and realized/unrealized P&L rollups, with an as_of open-position freshness clock), the data_as_of freshness timestamp (the open-position data's latest /positions snapshot, else last completed sync; the snapshot advances only open positions, so resolved/closed aggregates still date to the last full sync), and a freshness_note describing the point-in-time snapshot semantics. The path accepts an Ethereum wallet address (0x...), a known trader username, or a trd_-prefixed trader ID emitted by this API. position_summary is omitted when the trader is not in the local database; unknown lookups return 200 with sync_status 'unknown' on the nested trader (no 404). Append .md to the path for the Markdown rendering.