Improve JSDoc comments with cross-references and clarifications (#254)

Key improvements:
- Add `{@link}` cross-references throughout the codebase to make API
  documentation navigable and help AI models understand relationships
- Use `{@link module!Export}` syntax for cross-module references
- Add backticks for inline code formatting (`ResizeObserver`, `App`, etc)
- Fix `PostMessageTransport` examples to show required two-argument form
- Clarify `onteardown` callback return type requirement
- Document React hooks cleanup behavior and Strict Mode considerations
- Add tool visibility example for `registerAppTool`
- Add CSP example for `registerAppResource`
- Fix notification direction documentation in `spec.types.ts`

TypeDoc config migrated from `typedoc.json` to `typedoc.config.mjs` to:
- Support custom `@description` block tag
- Add `intentionallyNotExported` for internal types
- Include `src/server/index.ts` entry point

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

src/react/useDocumentTheme.ts

@@ -5,11 +5,13 @@ import { McpUiTheme } from "../types";
 /**
  * React hook that provides the current document theme reactively.
  *
- * Uses a MutationObserver to watch for changes to the `data-theme` attribute
+ * Uses a `MutationObserver` to watch for changes to the `data-theme` attribute
  * or `class` on `document.documentElement`. When the theme changes (e.g., from
  * host context updates), the hook automatically re-renders your component with
  * the new theme value.
  *
+ * The `MutationObserver` is automatically disconnected when the component unmounts.
+ *
  * @returns The current theme ("light" or "dark")
  *
  * @example Conditionally render based on theme