chore(sonar): mechanical src/ cleanups — AsSpan, drop ContainsKey guard, simplify GetQuery (CA1846, CA1853, S2219)

- `SqlParseException.cs:90` (CA1846): `sql.Substring(0, 197)` →
  `sql.AsSpan(0, 197)` in the truncated-SQL diagnostic message. Avoids
  an allocation in an already cold exception path.

- `Snowflake/QueryBreakdown.cs:103` (CA1853): drop the redundant
  `Parameters.ContainsKey(...)` guard around `Parameters.Remove(...)`.
  `Dictionary<TKey,TValue>.Remove` is a no-op if the key is absent, so
  the guard only doubled the work and computed the key string twice.

- `LinqQueryBreakdown.cs:194` (S2219): collapse the now-stub
  `GetQuery<T>()` (every branch returned `GetEmptyQueryable<T>()` after
  the S1168 cleanup) to a single expression-bodied member. Updates the
  XML doc to describe the actual current behavior.

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

src/Strata.SqlTools.LinqToSql/Breakdowns/LinqQueryBreakdown.cs

@@ -185,33 +185,13 @@ public class LinqQueryBreakdown : QueryBreakdown
     /// Gets a LINQ to SQL query of the specified type based on this breakdown.
     /// </summary>
     /// <typeparam name="T">The entity type for the query.</typeparam>
-    /// <returns>An IQueryable of the specified type reconstructed from the breakdown; an empty queryable if the type doesn't match the original entity type or the original data source isn't available.</returns>
+    /// <returns>An empty queryable. Breakdown analysis is one-way; reconstruction requires the original provider, which is not preserved.</returns>
     /// <remarks>
-    /// This method attempts to reconstruct a LINQ query from the analyzed components (WHERE, ORDER BY, etc.).
-    /// If a data source (IQueryable) is available in the breakdown's OriginalExpression, it will be used.
-    /// Otherwise, returns an empty queryable — breakdown analysis is one-way; reconstruction requires the original provider.
+    /// Always returns an empty queryable today. A future version may reconstruct the LINQ query from
+    /// <see cref="OriginalExpression"/> when the provider is available; until then callers receive an
+    /// empty result rather than a null reference.
     /// </remarks>
-    public override IQueryable<T> GetQuery<T>() where T : class
-    {
-        if (OriginalExpression == null)
-        {
-            return GetEmptyQueryable<T>();
-        }
-
-        try
-        {
-            if (OriginalExpression is Expression && EntityType == typeof(T))
-            {
-                return GetEmptyQueryable<T>();
-            }
-
-            return GetEmptyQueryable<T>();
-        }
-        catch
-        {
-            return GetEmptyQueryable<T>();
-        }
-    }
+    public override IQueryable<T> GetQuery<T>() where T : class => GetEmptyQueryable<T>();
 
     /// <summary>
     /// Get and empty queryable of T

src/Strata.SqlTools.Snowflake/Breakdowns/QueryBreakdown.cs

@@ -100,10 +100,7 @@ public class QueryBreakdown : SqlServerQueryBreakdown
         base.AddParameter(colonName.TrimStart(':', '@'), value);
 
         // Add both formats to dictionary for compatibility
-        if (Parameters.ContainsKey($"@{colonName.TrimStart(':', '@')}"))
-        {
-            Parameters.Remove($"@{colonName.TrimStart(':', '@')}");
-        }
+        Parameters.Remove($"@{colonName.TrimStart(':', '@')}");
         Parameters[colonName] = value;
         Parameters[atName] = value;
     }

src/Strata.SqlTools.SqlServer/Exceptions/SqlParseException.cs

@@ -87,7 +87,7 @@ public class SqlParseException : Exception
         }
         else
         {
-            sb.AppendLine($"SQL (truncated): {sql.Substring(0, 197)}...");
+            sb.AppendLine($"SQL (truncated): {sql.AsSpan(0, 197)}...");
         }
 
         return sb.ToString();