Add trading session helpers and extend ThrottledHistoryUpdater (#25)

* Add trading session helpers and extend ThrottledHistoryUpdater

Introduce mt5cli.trading with mt5_trading_session() for Mt5TradingClient
lifecycle management and reusable operational helpers for position-side
detection, margin/volume sizing, and protective order price derivation.

Extend ThrottledHistoryUpdater to validate inputs before updates and to
optionally suppress ValueError, OSError, and missing-method errors without
advancing the throttle timestamp.

Export the new helpers from mt5cli.__init__, add unit tests with mocked
clients, and document migration guidance for downstream projects such as
mteor.

Co-authored-by: Daichi Narushima <dceoy@users.noreply.github.com>

* Narrow ThrottledHistoryUpdater suppress_errors handling (#27)

* Narrow ThrottledHistoryUpdater suppress_errors for MT5 capability only

Remove broad AttributeError/TypeError handling from recoverable errors.
Add _is_mt5_client_capability_error() to detect missing history API methods
or non-callable client attributes by message and attribute name.

Generic AttributeError/TypeError values always propagate even when
suppress_errors=True. Update docs and tests accordingly.

Co-authored-by: Daichi Narushima <dceoy@users.noreply.github.com>

* Detect non-callable history client methods in suppress_errors

Address review feedback: when a history API attribute exists but is not
callable, Python raises a generic TypeError. Inspect the traceback for
mt5cli.history client call sites so these capability mismatches are still
suppressed without matching all TypeError values.

Co-authored-by: Daichi Narushima <dceoy@users.noreply.github.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Daichi Narushima <dceoy@users.noreply.github.com>

* Address PR review feedback on trading helpers

- Resolve history module path once at import time
- Only treat non-callable TypeErrors as capability errors at the raise site
- Validate SL/TP ratios in determine_order_limits
- Add tests for margin_free edge cases, body-raise shutdown, and internal TypeError propagation
- Clarify ThrottledHistoryUpdater suppress_errors docs
- Split README migration example into trading vs read-only history sessions

Co-authored-by: Daichi Narushima <dceoy@users.noreply.github.com>

* Tighten protective ratio validation and clamp negative margin_free

Add _require_protective_ratio enforcing 0 <= ratio < 1 for SL/TP limits so
a ratio of 1.0 cannot produce zero protective prices. Clamp negative
margin_free to 0.0 in calculate_margin_and_volume before sizing.

Add boundary and negative-margin tests; document constraints in trading API
docs.

Co-authored-by: Daichi Narushima <dceoy@users.noreply.github.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Daichi Narushima <dceoy@users.noreply.github.com>

docs/api/index.md

@@ -18,6 +18,10 @@ Utility module providing constants, enums, Click parameter types, and helper fun
 
 Programmatic SDK for read-only MetaTrader 5 data collection. Returns pandas DataFrames and provides `collect_history` for SQLite bulk collection.
 
+### [Trading](trading.md)
+
+Trading-capable session management and operational helpers built on `pdmt5.Mt5TradingClient`. Complements the read-only SDK without changing existing `Mt5CliClient` behavior.
+
 ### [History Collection (SQLite)](history.md)
 
 SQLite storage helpers for the `collect-history` command schema, incremental updates, deduplication, indexes, and optional views.
@@ -28,8 +32,9 @@ The package follows a simple architecture built on top of pdmt5:
 
 1. **CLI Layer** (`cli.py`): Typer application with subcommands that delegate to the SDK and export results.
 2. **SDK Layer** (`sdk.py`): Read-only data access functions, `Mt5CliClient`, and `collect_history` orchestration.
-3. **Utils Layer** (`utils.py`): Constants, enums, custom Click parameter types, parsing helpers, and format detection/export utilities.
-4. **Data Layer** (via `pdmt5`): Uses `Mt5DataClient` and `Mt5Config` from the pdmt5 package for all MetaTrader 5 data access.
+3. **Trading Layer** (`trading.py`): Trading-capable sessions and operational helpers on `Mt5TradingClient`.
+4. **Utils Layer** (`utils.py`): Constants, enums, custom Click parameter types, parsing helpers, and format detection/export utilities.
+5. **Data Layer** (via `pdmt5`): Uses `Mt5DataClient`, `Mt5TradingClient`, and `Mt5Config` from the pdmt5 package for MetaTrader 5 access.
 
 ## Usage Guidelines