RFC: A tag for customizing IntelliSense tooltips

In https://github.com/microsoft/tsdoc/issues/8#issuecomment-510733582 @bookmoons said:

Suggested in microsoft/vscode#77261 something like @extended and @extendedExample that's intended to land in docs but not be shown in smaller contexts like IntelliSense.

/**
 * Take over the specified world.
 * 
 * @param world - The world to dominate.
 * 
 * @remarks
 * Optimizes for minimum loss of life, minimum reputation harm, and maximum deviousness.
 * Leverages all available capital and human resources without remorse.
 *
 * @extended
 * The development of this procedure began with the Sumerian kings.
 * [... long history ...]
 * 
 * @extendedExample
 * // Example of error handling based on the latest best practices
 * while (!retired) {
 *   try { takeOverWorld(earth) } catch (error) {
 *     if (error instanceof InsurrectionError) squashInsurrection()
 *     else if (error instanceof CoupError) decimateCoup()
 *     else if (error instanceof GlobalThermonuclearWarError) retire()
 *     [.. long example list .. ]
 *   }
 * }
 *
 * @beta
 */
export function takeOverWorld(world: World): void;

I've opened this issue so we can have a more focused discussion.

Start by reviewing the linked TSDoc comment and the referenced microsoft/vscode#77261 discussion to understand the proposed @extended and @extendedExample tags. Determine the intended syntax, parsing behavior, and how these sections should be excluded from IntelliSense while remaining available in generated documentation. Done means the project has an agreed specification for the tag behavior.