Add MCP conformance test coverage (#435)

<!-- Provide a brief summary of your changes -->

## Motivation and Context

1. The currently failing checks are commented out in `ConformanceTest`,
see the TODOs.
2. I added detailed logging for Gradle task, Server, and Client to allow
easier output reading when viewing tests results outside of IDE.
3. As a future improvement, instead of hard-coding scenarios, we can get
them with `npx @modelcontextprotocol/conformance list` and run all of
them.
4. The conformance framework writes its result into
`kotlin-sdk-test/results` directory and contains JSONs like the one
below:
```json
[
  {
    "id": "mcp-client-initialization",
    "name": "MCPClientInitialization",
    "description": "Validates that MCP client properly initializes with server",
    "status": "SUCCESS",
    "timestamp": "2025-11-28T14:38:36.718Z",
    "specReferences": [
      {
        "id": "MCP-Lifecycle",
        "url": "https://modelcontextprotocol.io/specification/2025-06-18/basic/lifecycle"
      }
    ],
    "details": {
      "protocolVersionSent": "2025-06-18",
      "expectedSpecVersion": "2025-06-18",
      "versionMatch": true,
      "clientName": "kotlin-conformance-client",
      "clientVersion": "1.0.0"
    }
  },
  {
    "id": "server-info",
    "name": "ServerInfo",
    "description": "Test server info returned to client",
    "status": "INFO",
    "timestamp": "2025-11-28T14:38:36.718Z",
    "specReferences": [
      {
        "id": "MCP-Lifecycle",
        "url": "https://modelcontextprotocol.io/specification/2025-06-18/basic/lifecycle"
      }
    ],
    "details": {
      "serverName": "test-server",
      "serverVersion": "1.0.0"
    }
  }
]
```
As another future improvement, we can do somethig with these JSON files,
like putting them into a job summary on GitHub.

5. The client test also generated stderr.txt file in
`kotlin-sdk-test/results/initialize-.......` which contains errors
because it tries to call a tool. I haven't investigated if it's just the
way I wrote the client or related to `StreamableHttpClientTransport`.
6. The server is the simplified version of the existing server for
Kotlin<--->Typescript tests. If conformance tests extend significantly,
we can either combine the server implementations or ditch the
integration tests.

## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->

## Breaking Changes
<!-- Will users need to update their code or configurations? -->

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

---------

Co-authored-by: Konstantin Pavlov <1517853+kpavlov@users.noreply.github.com>

.github/workflows/build.yml

@@ -41,6 +41,7 @@ jobs:
             clean \
             ktlintCheck \
             build \
+            -x :conformance-test:test \
             koverLog koverHtmlReport \
             publishToMavenLocal \
             -Pversion=0.0.1-SNAPSHOT

.github/workflows/conformance.yml

@@ -0,0 +1,50 @@
+name: Conformance Tests
+
+on:
+  workflow_dispatch:
+  pull_request:
+    branches: [ main ]
+  push:
+    branches: [ main ]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  # Cancel only when the run is NOT on `main` branch
+  cancel-in-progress: ${{ github.ref != 'refs/heads/main'  }}
+
+jobs:
+  run-conformance:
+    runs-on: macos-latest-xlarge
+    name: Run Conformance Tests
+    timeout-minutes: 20
+    env:
+      JAVA_OPTS: "-Xmx8g -Dfile.encoding=UTF-8 -Djava.awt.headless=true -Dkotlin.daemon.jvm.options=-Xmx6g"
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Set up JDK 21
+        uses: actions/setup-java@v5
+        with:
+          java-version: '21'
+          distribution: 'temurin'
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '24.11.1'
+
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@v5
+        with:
+          add-job-summary: 'always'
+          cache-read-only: true
+
+      - name: Run Conformance Tests
+        run: ./gradlew --no-daemon :conformance-test:test
+
+      - name: Upload Conformance Results
+        if: ${{ !cancelled() }}
+        uses: actions/upload-artifact@v5
+        with:
+          name: conformance-results
+          path: conformance-test/results/

.github/workflows/gradle-publish.yml

@@ -34,7 +34,7 @@ jobs:
         uses: gradle/actions/setup-gradle@v5
 
       - name: Clean Build with Gradle
-        run: ./gradlew clean build
+        run: ./gradlew clean build -x :conformance-test:test
 
       - name: Publish to Maven Central Portal
         id: publish