Removes the 13 AddXxxFilter extension methods on IMcpServerBuilder that were deprecated under diagnostic MCP9002 in favor of WithRequestFilters() and WithMessageFilters().

Changes

• McpServerBuilderExtensions.cs — Deleted the MCP9002-marked methods: AddListResourceTemplatesFilter, AddListToolsFilter, AddCallToolFilter, AddListPromptsFilter, AddGetPromptFilter, AddListResourcesFilter, AddReadResourceFilter, AddCompleteFilter, AddSubscribeToResourcesFilter, AddUnsubscribeFromResourcesFilter, AddSetLoggingLevelFilter, AddIncomingMessageFilter, AddOutgoingMessageFilter

• Obsoletions.cs — Replaced MCP9002 constants with a comment recording what the ID was used for, preventing accidental reuse:

  // MCP9002 was used for the AddXxxFilter extension methods on IMcpServerBuilder that were superseded by
  // WithMessageFilters() and WithRequestFilters(). The APIs were removed; do not reuse this diagnostic ID.

• docs/list-of-diagnostics.md — Added an Obsolete APIs section documenting all MCP9### diagnostics issued to date, including whether each remains in place or has been removed:

  Diagnostic ID	Status	Description
  MCP9001	In place	EnumSchema/LegacyTitledEnumSchema deprecated per spec 2025-11-25
  MCP9002	Removed	AddXxxFilter on IMcpServerBuilder superseded by WithRequestFilters()/WithMessageFilters()

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