chore(cpp): remove dead TdxSnapshotTradeTick struct (#227) (#232)

No typed array type, no free function, already removed from the Go SDK.
Removes the struct from thetadx.h, the C++ alias from thetadx.hpp,
and the README table row.

Fixes #227

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: userFRM

sdks/cpp/README.md

@@ -254,7 +254,6 @@ All endpoints return fully typed C++ structs. No raw JSON.
 | `IvTick` | ms_of_day, implied_volatility, iv_error, date, **expiration, strike, right** | IV-only endpoints |
 | `PriceTick` | ms_of_day, price, date | Index price endpoints |
 | `MarketValueTick` | ms_of_day, market_cap, shares_outstanding, enterprise_value, book_value, free_float, date, **expiration, strike, right** | Market value endpoints |
-| `SnapshotTradeTick` | ms_of_day, sequence, size, condition, price, date, **expiration, strike, right** | Snapshot trade endpoints |
 | `OptionContract` | root, expiration, strike, right | option_list_contracts |
 | `CalendarDay` | date, is_open, open_time, close_time, status | Calendar endpoints |
 | `InterestRateTick` | ms_of_day, rate, date | Interest rate endpoints |

sdks/cpp/include/thetadx.h

@@ -193,18 +193,6 @@ TDX_ALIGN64_BEGIN typedef struct {
     double midpoint;
 } TdxQuoteTick TDX_ALIGN64_END;
 
-TDX_ALIGN64_BEGIN typedef struct {
-    int32_t ms_of_day;
-    int32_t sequence;
-    int32_t size;
-    int32_t condition;
-    double price;
-    int32_t date;
-    int32_t expiration;
-    double strike;
-    int32_t right;
-} TdxSnapshotTradeTick TDX_ALIGN64_END;
-
 TDX_ALIGN64_BEGIN typedef struct {
     int32_t ms_of_day;
     int32_t sequence;

sdks/cpp/include/thetadx.hpp

@@ -38,7 +38,6 @@ using OpenInterestTick = TdxOpenInterestTick;
 using MarketValueTick = TdxMarketValueTick;
 using CalendarDay = TdxCalendarDay;
 using InterestRateTick = TdxInterestRateTick;
-using SnapshotTradeTick = TdxSnapshotTradeTick;
 using TradeQuoteTick = TdxTradeQuoteTick;
 // OptionContract uses std::string for root to avoid use-after-free.
 // The C FFI TdxOptionContract uses a raw char* that is freed with the array,