Fix decimal separator format in calculator tool tests (#315)

## Changes
- Updated `DecimalFormatSymbols` to use period as decimal separator
(Locale.US)
- Fixed test expectations in `testComplexInputSchemaTool`:
  - `formattedResult`: `"11,000"` → `"11.000"`
- `tags`: Added actual test values `["test", "calculator",
"integration"]`
- Fixed test expectations in `testComplexNestedSchema`:
  - `formattedResult`: `"0,00"` → `"0.00"`

## Motivation
1. **Standard Decimal Notation**: Using a comma as a decimal separator
could be confusing as it's commonly used for thousands separators in
many locales. Standardizing on the period (`.`) follows international
conventions and makes the output clearer.

2. **Test Data Correction**: During the Validate PR workflow for #289,
discovered that the `tags` array in the `expectedContent` variable of
`testComplexInputSchemaTool()` was incorrectly set to an empty array,
which didn't match the actual input values being tested.

---------

Co-authored-by: MAERYO <maeryo@hanwha.com>

kotlin-sdk-test/src/jvmTest/kotlin/io/modelcontextprotocol/kotlin/sdk/integration/kotlin/AbstractToolIntegrationTest.kt

@@ -289,7 +289,7 @@ abstract class AbstractToolIntegrationTest : KotlinTestBase() {
             }
 
             val pattern = if (precision > 0) "0." + "0".repeat(precision) else "0"
-            val symbols = DecimalFormatSymbols(Locale.US).apply { decimalSeparator = ',' }
+            val symbols = DecimalFormatSymbols(Locale.US).apply { decimalSeparator = '.' }
             val df = DecimalFormat(pattern, symbols).apply { isGroupingUsed = false }
             val formattedResult = df.format(result)
 
@@ -482,7 +482,7 @@ abstract class AbstractToolIntegrationTest : KotlinTestBase() {
                   "a" : 5.5,
                   "b" : 2.0,
                   "result" : 11.0,
-                  "formattedResult" : "11,000",
+                  "formattedResult" : "11.000",
                   "precision" : 3,
                   "tags" : ["test", "calculator", "integration"]
                 }
@@ -633,7 +633,7 @@ abstract class AbstractToolIntegrationTest : KotlinTestBase() {
               "a": 0.0,
               "b": 0.0,
               "result": 0.0,
-              "formattedResult": "0,00",
+              "formattedResult": "0.00",
               "precision": 2,
               "tags": []
             }