Replace Instant with String for lastModified in Annotations (#383)

Replace `Instant` with `String` for `lastModified` in `Annotations`

## Motivation and Context
To fix serialization/kotlin library version conflicts 

## How Has This Been Tested?
Unit test

## Breaking Changes
Yes

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [x] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->

Author: kpavlov

kotlin-sdk-core/api/kotlin-sdk-core.api

@@ -1,14 +1,14 @@
 public final class io/modelcontextprotocol/kotlin/sdk/Annotations {
 	public static final field Companion Lio/modelcontextprotocol/kotlin/sdk/Annotations$Companion;
-	public fun <init> (Ljava/util/List;Lkotlin/time/Instant;Ljava/lang/Double;)V
+	public fun <init> (Ljava/util/List;Ljava/lang/String;Ljava/lang/Double;)V
 	public final fun component1 ()Ljava/util/List;
-	public final fun component2 ()Lkotlin/time/Instant;
+	public final fun component2 ()Ljava/lang/String;
 	public final fun component3 ()Ljava/lang/Double;
-	public final fun copy (Ljava/util/List;Lkotlin/time/Instant;Ljava/lang/Double;)Lio/modelcontextprotocol/kotlin/sdk/Annotations;
-	public static synthetic fun copy$default (Lio/modelcontextprotocol/kotlin/sdk/Annotations;Ljava/util/List;Lkotlin/time/Instant;Ljava/lang/Double;ILjava/lang/Object;)Lio/modelcontextprotocol/kotlin/sdk/Annotations;
+	public final fun copy (Ljava/util/List;Ljava/lang/String;Ljava/lang/Double;)Lio/modelcontextprotocol/kotlin/sdk/Annotations;
+	public static synthetic fun copy$default (Lio/modelcontextprotocol/kotlin/sdk/Annotations;Ljava/util/List;Ljava/lang/String;Ljava/lang/Double;ILjava/lang/Object;)Lio/modelcontextprotocol/kotlin/sdk/Annotations;
 	public fun equals (Ljava/lang/Object;)Z
 	public final fun getAudience ()Ljava/util/List;
-	public final fun getLastModified ()Lkotlin/time/Instant;
+	public final fun getLastModified ()Ljava/lang/String;
 	public final fun getPriority ()Ljava/lang/Double;
 	public fun hashCode ()I
 	public fun toString ()Ljava/lang/String;

kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types.kt

@@ -17,8 +17,6 @@ import kotlin.concurrent.atomics.AtomicLong
 import kotlin.concurrent.atomics.ExperimentalAtomicApi
 import kotlin.concurrent.atomics.incrementAndFetch
 import kotlin.jvm.JvmInline
-import kotlin.time.ExperimentalTime
-import kotlin.time.Instant
 
 public const val LATEST_PROTOCOL_VERSION: String = "2025-03-26"
 
@@ -302,6 +300,7 @@ public data class JSONRPCError(val code: ErrorCode, val message: String, val dat
 public sealed interface NotificationParams : WithMeta
 
 /* Cancellation */
+
 /**
  * This notification can be sent by either side to indicate that it is cancelling a previously issued request.
  *
@@ -334,6 +333,7 @@ public data class CancelledNotification(override val params: Params) :
 }
 
 /* Initialization */
+
 /**
  * Describes the name and version of an MCP implementation.
  */
@@ -531,6 +531,7 @@ public data class InitializedNotification(override val params: Params = Params()
 }
 
 /* Ping */
+
 /**
  * A ping, issued by either the server or the client, to check that the other party is still alive.
  * The receiver must promptly respond, or else it may be disconnected.
@@ -564,6 +565,7 @@ public sealed interface ProgressBase {
 }
 
 /* Progress notifications */
+
 /**
  * Represents a progress notification.
  *
@@ -623,6 +625,7 @@ public data class ProgressNotification(override val params: Params) :
 }
 
 /* Pagination */
+
 /**
  * Represents a request supporting pagination.
  */
@@ -650,6 +653,7 @@ public sealed interface PaginatedResult : RequestResult {
 }
 
 /* Resources */
+
 /**
  * The contents of a specific resource or sub-resource.
  */
@@ -892,6 +896,7 @@ public data class ResourceUpdatedNotification(override val params: Params) : Ser
 }
 
 /* Prompts */
+
 /**
  * Describes an argument that a prompt can accept.
  */
@@ -1115,8 +1120,7 @@ public data class Annotations(
     /**
      * The moment the resource was last modified.
      */
-    @OptIn(ExperimentalTime::class)
-    val lastModified: Instant?,
+    val lastModified: String?,
     /**
      * Describes how important this data is for operating the server.
      *
@@ -1162,6 +1166,7 @@ public data class PromptListChangedNotification(override val params: Params = Pa
 }
 
 /* Tools */
+
 /**
  * Additional properties describing a Tool to clients.
  *
@@ -1345,6 +1350,7 @@ public data class ToolListChangedNotification(override val params: Params = Para
 }
 
 /* Logging */
+
 /**
  * The severity of a log message.
  */
@@ -1404,6 +1410,7 @@ public data class LoggingMessageNotification(override val params: Params) : Serv
 }
 
 /* Sampling */
+
 /**
  * Hints to use for model selection.
  */
@@ -1648,6 +1655,7 @@ public data class CompleteResult(val completion: Completion, override val _meta:
 }
 
 /* Roots */
+
 /**
  * Represents a root directory or file that the server can operate on.
  */

kotlin-sdk-core/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/TypesTest.kt

@@ -7,7 +7,6 @@ import kotlin.test.assertIs
 import kotlin.test.assertNotEquals
 import kotlin.test.assertTrue
 import kotlin.time.ExperimentalTime
-import kotlin.time.Instant
 
 class TypesTest {
 
@@ -243,15 +242,15 @@ class TypesTest {
     fun `should serialize and deserialize annotations correctly`() {
         val annotations = Annotations(
             audience = listOf(Role.assistant),
-            lastModified = Instant.parse("2025-06-18T00:00:00Z"),
+            lastModified = "2025-06-18T00:00:00Z",
             priority = 0.5,
         )
 
         val json = McpJson.encodeToString(annotations)
         val decoded = McpJson.decodeFromString<Annotations>(json)
 
         assertEquals(listOf(Role.assistant), decoded.audience)
-        assertEquals(Instant.parse("2025-06-18T00:00:00Z"), decoded.lastModified)
+        assertEquals("2025-06-18T00:00:00Z", decoded.lastModified)
         assertEquals(0.5, decoded.priority)
     }
 

kotlin-sdk-server/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/server/WebSocketMcpKtorServerExtensions.kt

@@ -71,7 +71,7 @@ internal suspend fun WebSocketServerSession.mcpWebSocketEndpoint(block: () -> Se
     try {
         session = server.createSession(transport)
         awaitCancellation()
-    } catch (e: CancellationException) {
+    } catch (_: CancellationException) {
         session?.close()
     }
 }