Allow MCP save_note tool to update existing notes

Pavan Kumar Sadashivrequested to merge
gitlab-community/gitlab-org/gitlab:hrlpavan-632622-mcp-save-note-update into master

What does this MR do and why?

Allows the MCP save_note tool to edit an existing comment via method: 'update_note' or when note_id is passed, routing to the updateNote GraphQL mutation (Mutations::Notes::Update::Note) instead of requiring agents to post a duplicate comment.

  • Adds update_note to SaveNoteService::METHOD_PARAMS (required: %i[body note_id]) and input_schema.
  • Defaults method to 'update_note' when note_id is provided without method or discussion_id.
  • Adds app/graphql/queries/mcp/notes/update_note.mutation.graphql and routes SaveNoteTool to updateNote with bare or Global ID note_id support.

Closes #632622

Merge request reports