refactor(query): extract shared Strata.SqlTools.Query model project

Moves the byte-identical 19-file ExpressionFactory/Query tree (duplicated
across Snowflake and SqlServer) into the new Strata.SqlTools.Query project
under the flat namespace Strata.SqlTools.Query. Both dialect projects now
reference the shared project; the Snowflake copies are deleted.

Also folds in the IDE0028 fix on CalculationFilterGroup.GetValidFilters
(collection expression []), which resolves both new-code IDE0028 smells
in one place now that there is a single copy.

Eliminates the 63 new duplicate lines flagged on the PR and removes the
largest contributor to the project's 11.1% duplication density. No
behavioral change: the moved types are identical to the originals.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Strata.SqlTools.Query/SqlResponse.cs

@@ -0,0 +1,13 @@
+namespace Strata.SqlTools.Query;
+
+public class SqlResponse
+{
+    public string SqlQuery { get; }
+    public IEnumerable<KeyValuePair<string, object>> Parameters { get; }
+
+    public SqlResponse(string sqlQuery, IEnumerable<KeyValuePair<string, object>> parameters)
+    {
+        SqlQuery = sqlQuery;
+        Parameters = parameters;
+    }
+}