test: reduce test_trading.py duplication with parametrize (#64)

* test: reduce test_trading.py duplication with parametrize

Collapse repetitive individual tests in test_trading.py into
parametrized equivalents, cutting 267 lines without losing any cases.

- TestExtractTickPrice: 13 tests → 2 parametrized (×3 valid, ×10 None)
- TestEstimateOrderMargin: 4 invalid-margin tests → 1 parametrized ×4;
  nan/inf volume tests → 1 parametrized ×2
- TestNormalizeOrderVolume: multi-assert bodies split into parametrized
  cases for non-finite volume and constraints
- TestVolumeAndExecution: 9 place_market_order retcode tests → 1 ×11;
  5 update_sltp retcode tests → 1 ×5
- test_calculate_trailing_stop_updates_missing_symbol_digits:
  inline double-assert body → 1 parametrized ×2

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* test: further reduce test_trading.py duplication with parametrize

Merge six broker stop-level tests into two parametrized tests, collapse
two default-digits fallback tests and three symbol-filter zero-margin
tests into one each.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* test: address claude[bot] review on PR #64

- Consolidate _MISSING_RETCODE sentinel to one line with corrected comment
- Add comment explaining ids list is required for deterministic node IDs
- Document intentional narrower retcode coverage in update_sltp test

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* test: reduce duplication in test_sdk, test_history, test_contracts

- TestBuildConfigWholeDollarEnv: 3 field tests (server/password/path) → 1
  parametrized ×3
- TestResolveAccountSpec: whole-dollar expand/no-expand pair → 1 parametrized ×2
- test_normalize_mt5_exception_maps_types: 2 isinstance asserts → parametrized ×2
- test_resolve_history_tick_flags_invalid: 2 pytest.raises blocks → parametrized ×2

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: agent <agent@localhost>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_sdk.py

@@ -1938,29 +1938,28 @@ class TestResolveAccountSpec:
         assert [a.server for a in resolved] == ["Shared", "Fixed"]
         assert all(a.timeout == 1000 for a in resolved)
 
-    def test_resolve_account_spec_with_whole_dollar_env(
+    @pytest.mark.parametrize(
+        ("allow_whole_dollar_env", "expected"),
+        [
+            (True, "secret"),
+            (False, "$MT5_PASSWORD"),
+        ],
+    )
+    def test_resolve_account_spec_whole_dollar_password(
         self,
         monkeypatch: pytest.MonkeyPatch,
+        allow_whole_dollar_env: bool,
+        expected: str,
     ) -> None:
-        """Account spec expands $ENV_NAME when allow_whole_dollar_env=True."""
+        """Test resolve_account_spec expands $ENV_NAME password only with opt-in."""
         monkeypatch.setenv("MT5_PASSWORD", "secret")
         account = AccountSpec(symbols=["EURUSD"], password="$MT5_PASSWORD")
 
-        resolved = resolve_account_spec(account, allow_whole_dollar_env=True)
+        resolved = resolve_account_spec(
+            account, allow_whole_dollar_env=allow_whole_dollar_env
+        )
 
-        assert resolved.password == "secret"  # noqa: S105
-
-    def test_resolve_account_spec_whole_dollar_not_expanded_by_default(
-        self,
-        monkeypatch: pytest.MonkeyPatch,
-    ) -> None:
-        """Test resolve_account_spec leaves $ENV_NAME literal by default."""
-        monkeypatch.setenv("MT5_PASSWORD", "secret")
-        account = AccountSpec(symbols=["EURUSD"], password="$MT5_PASSWORD")
-
-        resolved = resolve_account_spec(account)
-
-        assert resolved.password == "$MT5_PASSWORD"  # noqa: S105
+        assert resolved.password == expected
 
     def test_resolve_account_specs_with_whole_dollar_env(
         self,
@@ -1994,38 +1993,27 @@ class TestResolveAccountSpec:
 class TestBuildConfigWholeDollarEnv:
     """Tests for build_config with allow_whole_dollar_env."""
 
-    def test_build_config_substitutes_server_with_opt_in(
+    @pytest.mark.parametrize(
+        ("env_var", "field", "env_value"),
+        [
+            ("MT5_SERVER", "server", "Broker-Demo"),
+            ("MT5_PASSWORD", "password", "secret"),
+            ("MT5_PATH", "path", "/opt/mt5/terminal64.exe"),
+        ],
+    )
+    def test_build_config_substitutes_field_with_opt_in(
         self,
         monkeypatch: pytest.MonkeyPatch,
+        env_var: str,
+        field: str,
+        env_value: str,
     ) -> None:
-        """build_config expands $ENV_NAME server when allow_whole_dollar_env=True."""
-        monkeypatch.setenv("MT5_SERVER", "Broker-Demo")
+        """Test build_config expands $ENV_NAME fields when opt-in is enabled."""
+        monkeypatch.setenv(env_var, env_value)
 
-        config = build_config(server="$MT5_SERVER", allow_whole_dollar_env=True)
+        config = build_config(**{field: f"${env_var}"}, allow_whole_dollar_env=True)  # type: ignore[arg-type]
 
-        assert config.server == "Broker-Demo"
-
-    def test_build_config_substitutes_password_with_opt_in(
-        self,
-        monkeypatch: pytest.MonkeyPatch,
-    ) -> None:
-        """build_config expands $ENV_NAME password when allow_whole_dollar_env=True."""
-        monkeypatch.setenv("MT5_PASSWORD", "secret")
-
-        config = build_config(password="$MT5_PASSWORD", allow_whole_dollar_env=True)
-
-        assert config.password == "secret"  # noqa: S105
-
-    def test_build_config_substitutes_path_with_opt_in(
-        self,
-        monkeypatch: pytest.MonkeyPatch,
-    ) -> None:
-        """Test build_config expands $ENV_NAME path when allow_whole_dollar_env=True."""
-        monkeypatch.setenv("MT5_PATH", "/opt/mt5/terminal64.exe")
-
-        config = build_config(path="$MT5_PATH", allow_whole_dollar_env=True)
-
-        assert config.path == "/opt/mt5/terminal64.exe"
+        assert getattr(config, field) == env_value
 
     def test_build_config_leaves_dollar_literal_by_default(
         self,