MtApi5: custom symbols support (CustomSymbol*, CustomRates*, CustomTicks*)

[biohazardxxx]

Summary

Adds MT5 custom symbols support to the MtApi5 connector. MQL5 can create synthetic instruments and feed them history/ticks natively (CustomSymbolCreate, CustomRatesUpdate, CustomTicksAdd, …) but none of it was reachable from the .NET client. This adds 11 CustomSymbol* / CustomRates* / CustomTicks* functions end-to-end.

C# client (MtApi5) — 11 methods on MtApi5Client:

Command id	Method
340	bool CustomSymbolCreate(string symbolName, string symbolPath = "", string symbolOrigin = "")
341	bool CustomSymbolDelete(string symbolName)
342	bool CustomSymbolSetDouble(string symbolName, ENUM_SYMBOL_INFO_DOUBLE propertyId, double value)
343	bool CustomSymbolSetInteger(string symbolName, ENUM_SYMBOL_INFO_INTEGER propertyId, long value)
344	bool CustomSymbolSetString(string symbolName, ENUM_SYMBOL_INFO_STRING propertyId, string value)
345	int CustomRatesDelete(string symbolName, DateTime from, DateTime to)
346	int CustomRatesReplace(string symbolName, DateTime from, DateTime to, MqlRates[] rates)
347	int CustomRatesUpdate(string symbolName, MqlRates[] rates)
348	int CustomTicksAdd(string symbolName, MqlTick[] ticks)
349	int CustomTicksDelete(string symbolName, long fromMsc, long toMsc)
350	int CustomTicksReplace(string symbolName, long fromMsc, long toMsc, MqlTick[] ticks)

MQL5 EA (mq5/MtApi5.mq5) — 11 Execute_Custom* handlers + ADD_EXECUTOR registrations (ids 340–350) + new JsonToMqlRates / JsonToMqlTick / JsonToMqlRatesArray / JsonToMqlTickArray parse helpers. mq5/MtApi5.ex5 recompiled and included.

TestClient — a CustomSymbolTest button that runs the full lifecycle manually (create → set int/double/string properties → CustomRatesUpdate 3 bars → SymbolSelect → CustomTicksAdd 2 ticks → CustomTicksDelete → CustomRatesDelete → deselect → CustomSymbolDelete, each result logged).

Implementation notes

• Command ids 340–350 match exactly between MtApi5/MtProtocol/Mt5CommandType.cs and the mq5 ADD_EXECUTOR registrations.
• Struct-array wire format mirrors the existing EA→client serializers in reverse: MqlRates[] uses the MqlRatesToJson keys (mt_time, open, high, low, close, tick_volume, spread, real_volume; datetimes as unix seconds), MqlTick[] uses the MqlTickToJson keys plus TimeMsc (Time, TimeMsc, Bid, Ask, Last, Volume, VolumeReal, Flags); flags sent as uint, volume_real as double. The mq5 parse helpers use json.mqh with ZeroMemory on struct elements and follow the house pattern of JsonToMqlTradeRequest (null-check getValue(key) then read via the one-arg getters — the type-checked out-parameter getters in json.mqh don't work for numbers because the parser never sets JSON_NUMBER).
• MqlTick (C#) gained an additive public long time_msc property (the class previously only had second-resolution MtTime); serialization falls back to MtTime * 1000 when time_msc is 0, and the EA reconciles time/time_msc in both directions.
• Error semantics: bool commands propagate the raw native bool, int commands propagate the raw native return including -1 (success responses, no CreateErrorResponse mapping) — matching the calendar-PR philosophy (post-d8c459fd).
• Known limitation (pre-existing transport, not touched here): MT5Connector.cpp convertSystemString truncates inbound command payloads at 1000 wide chars (memcpy bounded by wcsnlen(..., 1000)), even though the EA-side buffer is 5000. Payloads with more than roughly 6 rates or 5–6 ticks per call get truncated at runtime and the EA answers "Failed to get payload". Callers must chunk large arrays: CustomRatesUpdate / CustomTicksAdd are incremental so chunking is semantically safe; a chunked CustomRatesReplace / CustomTicksReplace is not equivalent to one atomic call. The TestClient action keeps its arrays within this cap.
• Diff is purely additive; branch is based on dev and contains custom-symbols changes only.

Testing

• MtApi5 builds clean (Release, 0 warnings / 0 errors); MtApi5TestClient builds with 0 errors (only pre-existing nullability-pattern warnings).
• mq5/MtApi5.mq5 compiles via MetaEditor with "Result: 0 errors"; the recompiled MtApi5.ex5 is included.
• Not runtime-tested against a live MT5 terminal — verification was compile-level plus a manual wire-format review (payload/response JSON keys, datetime and flags/volume marshaling checked against both sides). The TestClient CustomSymbolTest button is provided for a live round-trip, which I'd recommend before merge.

🤖 Generated with Claude Code

[biohazardxxx]

Pushed a completing fix: MqlTickToJson never emitted time_msc and the MtTick protocol DTO had no field for it, so the C# MqlTick.time_msc added in this PR was always 0 on the receive path (CopyTicks/SymbolInfoTick). Now round-trips in both directions — verified live: millisecond timestamps populate for forex ticks (e.g. 1783588818147/…360/…372 within one second). Recompiled ex5 included.