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

src/Capability/Discovery/Discoverer.php

@@ -98,7 +98,7 @@ class Discoverer
                 $this->processFile($file, $discoveredCount);
             }
         } catch (\Throwable $e) {
-            $this->logger->error('Error during file finding process for MCP discovery', [
+            $this->logger->error('Error during file finding process for MCP discovery'.json_encode($e->getTrace(), \JSON_PRETTY_PRINT), [
                 'exception' => $e->getMessage(),
                 'trace' => $e->getTraceAsString(),
             ]);