refactor: remove dead code and obsolete examples (#76)

- Remove ToolChain, ResourceChain, PromptChain classes
- Remove Collection/Identifier/Metadata interfaces (only used by old Chains)
- Remove ToolCollectionInterface (unused)
- Delete obsolete examples 09-standalone-cli and 10-simple-http-transport
- Fix STDERR handling in bootstrap.php for web environments
- Clean up CHANGELOG.md

CHANGELOG.md

@@ -1,24 +1,3 @@
-CHANGELOG
-=========
+# Changelog
 
-0.1
----
-
- * Add Model Context Protocol (MCP) implementation for LLM-application communication
- * Add JSON-RPC based protocol handling with `JsonRpcHandler`
- * Add three core MCP capabilities:
-   - Resources: File-like data readable by clients (API responses, file contents)
-   - Tools: Functions callable by LLMs (with user approval)
-   - Prompts: Pre-written templates for specific tasks
- * Add multiple transport implementations:
-   - Symfony Console Transport for testing and CLI applications
-   - Stream Transport supporting Server-Sent Events (SSE) and HTTP streaming
-   - STDIO transport for command-line interfaces
- * Add capability chains for organizing features:
-   - `ToolChain` for tool management
-   - `ResourceChain` for resource management
-   - `PromptChain` for prompt template management
- * Add Server component managing transport connections
- * Add request/notification handlers for MCP operations
- * Add standardized interface enabling LLMs to interact with external systems
- * Add support for building LLM "plugins" with extra context capabilities
+All notable changes to `mcp/sdk` will be documented in this file.