## Description The mcp_server core module currently ships four in-tree submodules. This refactor removes them so they can be maintained as standalone companion projects, leaving core to ship only the runtime and its extension points (event subscribers on the SDK's events, the Tool plugin API, prompts, resources, and notifications contracts). Submodules being extracted: - mcp_server_tool_bridge (Tool API bridge) - mcp_server_examples (example plugins / echo tool / prompt configs) - mcp_server_ui (admin UI) - mcp_server_oauth (OAuth2 scope enforcement) Net change is approximately 215 insertions and 7788 deletions. ## Acceptance Criteria - [x] The four submodule directories (mcp_server_tool_bridge, mcp_server_examples, mcp_server_ui, mcp_server_oauth) are removed. - [x] README.md and AGENTS.md are rewritten to describe core only and point optional functionality at the companion projects. - [x] references/: the four docs covering only removed code (tool-api-bridge, tool-configuration, auth/tool-authentication, auth/metadata-discovery) are deleted, and the rest are trimmed to the core contract. - [x] .gitlab-ci.yml drops the mcp_server_oauth _PHPUNIT_EXTRA include and narrows _LENIENT_ALLOW_LIST to drupal/tool. - [x] composer.json drops the simple_oauth/simple_oauth_21 dev dependencies that only served the OAuth submodule tests. - [x] .cspell.json drops the dead mcp_server_examples config paths. - [x] A core-native echo tool fixture plus two prompt-config fixtures are ported into the mcp_server_test module so the core functional test preserves end-to-end coverage without depending on mcp_server_examples. ## Additional Context Work is implemented on branch `remove-in-tree-submodules` (commit 55647b8), targeting the `2.x` branch.