ai customizations: mcp marketplace (#297087)

* feat: enhance MCP list widget with gallery browsing and UI improvements

* Update customization: npm-i.json

* remove hook from tree

* Update customization: test.prompt.md

* feat: add MCP servers section to AI customization management

* refactor: remove unused IMcpGalleryService dependency and clean up marketplace button visibility logic

* feat: add underline style to last child of back link on hover in MCP list widget

* feat: enable opening MCP server details in the same editor group from the MCP list widget

* feat: add embedded MCP server detail view to AI customization management editor

* Update src/vs/workbench/contrib/chat/browser/aiCustomization/mcpListWidget.ts

Co-authored-by: Copilot <[email protected]>

* Update src/vs/workbench/contrib/chat/browser/aiCustomization/mcpListWidget.ts

Co-authored-by: Copilot <[email protected]>

* Update src/vs/workbench/contrib/chat/browser/aiCustomization/mcpListWidget.ts

Co-authored-by: Copilot <[email protected]>

* feat: enhance accessibility for back link in MCP list widget

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Co-authored-by: Copilot <[email protected]>