sample: kotlinlang mcp server (#713)

add new sample: kotlinlang mcp server with 2 tools
- search
- get_page

## How Has This Been Tested?
inspector/unit

## Breaking Changes
none

## 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

samples/kotlinlang-mcp-server/README.md

@@ -0,0 +1,105 @@
+# Kotlinlang MCP Server
+
+A Streamable HTTP MCP server that exposes the official
+[Kotlin documentation](https://kotlinlang.org/docs/) to LLM clients — full-text search via
+[Algolia](https://www.algolia.com/) plus page retrieval in markdown through kotlinlang.org's
+`_llms` endpoints.
+
+## Overview
+
+This sample demonstrates an MCP server that wraps a real external documentation source. It uses the
+recommended Streamable HTTP transport, supports multiple concurrent client sessions, and caches
+responses in memory to reduce upstream load. The server is intentionally read-only — it exposes two
+tools, no prompts, no resources.
+
+## Prerequisites
+
+- JDK 21+
+- Algolia credentials for `kotlinlang.org` (exported as environment variables, see
+  [Configuration](#configuration))
+
+## Build & Run
+
+```shell
+export ALGOLIA_APP_ID=...
+export ALGOLIA_API_KEY=...
+export ALGOLIA_INDEX_NAME=...
+
+./gradlew run
+```
+
+The server starts on `http://localhost:8080/mcp` by default.
+
+Connect with the [MCP Inspector](https://modelcontextprotocol.io/docs/tools/inspector):
+
+```shell
+npx @modelcontextprotocol/inspector
+```
+
+In the Inspector UI, select **Streamable HTTP** transport and enter `http://localhost:8080/mcp`.
+
+## MCP Capabilities
+
+### Tools
+
+| Name                  | Description                                                                                                                            |
+|-----------------------|----------------------------------------------------------------------------------------------------------------------------------------|
+| `search_kotlinlang`   | Full-text search across Kotlin documentation. Returns up to 5 results filtered to `/docs/` pages. Responses cached for 10 minutes.     |
+| `get_kotlinlang_page` | Fetches a documentation page as markdown via kotlinlang.org's `_llms` endpoint. Accepts a path relative to `/docs/`. Cached for 1 hour. |
+
+Example paths accepted by `get_kotlinlang_page`: `coroutines-overview`,
+`multiplatform/compose-multiplatform-and-jetpack-compose`. Leading/trailing slashes and an optional
+`.html` suffix are normalized before resolution.
+
+## Configuration
+
+| Variable             | Required | Default   | Description              |
+|----------------------|----------|-----------|--------------------------|
+| `ALGOLIA_APP_ID`     | yes      | —         | Algolia application ID   |
+| `ALGOLIA_API_KEY`    | yes      | —         | Algolia search API key   |
+| `ALGOLIA_INDEX_NAME` | yes      | —         | Algolia index name       |
+| `SERVER_PORT`        | no       | `8080`    | HTTP server port         |
+| `SERVER_HOST`        | no       | `0.0.0.0` | HTTP server bind address |
+
+The server does not provide fallback values for `ALGOLIA_*`. Startup fails if any of those
+variables are missing.
+
+## Docker
+
+Multi-stage build with Alpine-based images. Runs as a non-root user.
+
+```shell
+docker build -t kotlinlang-mcp-server .
+
+docker run \
+  -p 8080:8080 \
+  -e ALGOLIA_APP_ID=... \
+  -e ALGOLIA_API_KEY=... \
+  -e ALGOLIA_INDEX_NAME=... \
+  kotlinlang-mcp-server
+```
+
+## Connecting an MCP client
+
+Any MCP client that supports Streamable HTTP transport can connect:
+
+```json
+{
+  "mcpServers": {
+    "kotlinlang": {
+      "url": "http://localhost:8080/mcp"
+    }
+  }
+}
+```
+
+## Limitations
+
+This sample is intended **for demonstration only**. Before production use, consider:
+
+- **In-memory cache only** — cached data is lost on server restart.
+- **No authentication or authorization** — run behind a trusted proxy or restrict network access.
+- **No rate limiting** on outgoing requests to Algolia and kotlinlang.org.
+- **Permissive CORS** (`anyHost()`) — restrict to specific origins for any non-local deployment.
+- **Streamable HTTP only** — no STDIO transport for local-only usage.
+- **Tools only** — no MCP resources or prompts are exposed.