Prompt files provider API V2 (#286457)

* wip

* updates

* Apply suggestion from @Copilot

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* test

* dispose

* clean

* remove

* invalidate

* wip

* pr

* use enum

* PR

* clean

* more cleanup

* more cleanup

* more cleanup

* more cleanup

* more cleanup

* nit

* add optional metadata

* use new proposal

* clean

* clean

* nit

* v2

* yaml clean

* clean

* Update src/vs/workbench/api/common/extHostChatAgents2.ts

Co-authored-by: Martin Aeschlimann <martinae@microsoft.com>

* PR

* wip

* PR

* Update src/vs/base/common/yaml.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* add command

* pr

* PR

* PR

* PR

* clean

* PR

* use cache

* nit clean

* clean

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Martin Aeschlimann <martinae@microsoft.com>

src/vs/workbench/api/common/extHost.api.impl.ts

@@ -1960,6 +1960,9 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 			McpStdioServerDefinition2: extHostTypes.McpStdioServerDefinition,
 			McpToolAvailability: extHostTypes.McpToolAvailability,
 			SettingsSearchResultKind: extHostTypes.SettingsSearchResultKind,
+			CustomAgentChatResource: extHostTypes.CustomAgentChatResource,
+			InstructionsChatResource: extHostTypes.InstructionsChatResource,
+			PromptFileChatResource: extHostTypes.PromptFileChatResource,
 		};
 	};
 }