feat: add URL mode elicitation and typed schema definitions per MCP (#660)

Add URL mode elicitation support and typed `PrimitiveSchemaDefinition`
hierarchy to align with MCP specification 2025-11-25

closes #540 

## How Has This Been Tested?
unit/integration/conformance

## Breaking Changes
- `ElicitRequestParams` changed from `data class` to `sealed interface`.
A deprecated factory function preserves source compatibility for
`ElicitRequestParams(message, requestedSchema)`.
- `RequestedSchema.properties` changed from `JsonObject` to `Map<String,
PrimitiveSchemaDefinition>`.
- `ElicitRequest.requestedSchema` is deprecated, use `(params as
ElicitRequestFormParams).requestedSchema`.

## Types of changes
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [x] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed

integration-test/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/client/ClientTest.kt

@@ -10,6 +10,7 @@ import io.modelcontextprotocol.kotlin.sdk.shared.TransportSendOptions
 import io.modelcontextprotocol.kotlin.sdk.types.ClientCapabilities
 import io.modelcontextprotocol.kotlin.sdk.types.CreateMessageRequest
 import io.modelcontextprotocol.kotlin.sdk.types.CreateMessageResult
+import io.modelcontextprotocol.kotlin.sdk.types.ElicitRequestFormParams
 import io.modelcontextprotocol.kotlin.sdk.types.ElicitRequestParams
 import io.modelcontextprotocol.kotlin.sdk.types.ElicitResult
 import io.modelcontextprotocol.kotlin.sdk.types.EmptyJsonObject
@@ -35,6 +36,7 @@ import io.modelcontextprotocol.kotlin.sdk.types.Root
 import io.modelcontextprotocol.kotlin.sdk.types.RootsListChangedNotification
 import io.modelcontextprotocol.kotlin.sdk.types.SUPPORTED_PROTOCOL_VERSIONS
 import io.modelcontextprotocol.kotlin.sdk.types.ServerCapabilities
+import io.modelcontextprotocol.kotlin.sdk.types.StringSchema
 import io.modelcontextprotocol.kotlin.sdk.types.TextContent
 import io.modelcontextprotocol.kotlin.sdk.types.Tool
 import io.modelcontextprotocol.kotlin.sdk.types.ToolSchema
@@ -48,7 +50,6 @@ import kotlinx.coroutines.test.runTest
 import kotlinx.coroutines.withTimeout
 import kotlinx.serialization.json.buildJsonObject
 import kotlinx.serialization.json.put
-import kotlinx.serialization.json.putJsonObject
 import kotlin.coroutines.cancellation.CancellationException
 import kotlin.test.Test
 import kotlin.test.assertEquals
@@ -953,11 +954,7 @@ class ClientTest {
             serverSession.createElicitation(
                 message = "Please provide your GitHub username",
                 requestedSchema = ElicitRequestParams.RequestedSchema(
-                    properties = buildJsonObject {
-                        putJsonObject("name") {
-                            put("type", "string")
-                        }
-                    },
+                    properties = mapOf("name" to StringSchema()),
                     required = listOf("name"),
                 ),
             )
@@ -1061,11 +1058,7 @@ class ClientTest {
 
         val elicitationMessage = "Please provide your GitHub username"
         val requestedSchema = ElicitRequestParams.RequestedSchema(
-            properties = buildJsonObject {
-                putJsonObject("name") {
-                    put("type", "string")
-                }
-            },
+            properties = mapOf("name" to StringSchema()),
             required = listOf("name"),
         )
 
@@ -1076,7 +1069,8 @@ class ClientTest {
 
         client.setElicitationHandler { request ->
             assertEquals(elicitationMessage, request.params.message)
-            assertEquals(requestedSchema, request.params.requestedSchema)
+            val formParams = request.params as ElicitRequestFormParams
+            assertEquals(requestedSchema, formParams.requestedSchema)
 
             ElicitResult(
                 action = elicitationResultAction,