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/styles.ts

@@ -76,12 +76,12 @@ export function applyDocumentTheme(theme: McpUiTheme): void {
 /**
  * Apply host style variables as CSS custom properties on an element.
  *
- * This function takes the `variables` object from `McpUiHostContext.styles` and sets
+ * This function takes the `variables` object from {@link McpUiHostContext.styles} and sets
  * each CSS variable on the specified root element (defaults to `document.documentElement`).
  * This allows apps to use the host's theming values via CSS variables like
  * `var(--color-background-primary)`.
  *
- * @param styles - The styles object from `McpUiHostContext.styles.variables`
+ * @param styles - The style variables object from `McpUiHostContext.styles.variables`
  * @param root - The element to apply styles to (defaults to `document.documentElement`)
  *
  * @example Apply style variables from host context
@@ -123,10 +123,10 @@ export function applyHostStyleVariables(
  * self-hosted fonts, `@import` statements for Google Fonts or other font services,
  * or a combination of both.
  *
- * The styles are only injected once. Subsequent calls will not create duplicate
- * style tags.
+ * The styles are only injected once. Subsequent calls are no-ops and will not
+ * create duplicate style tags.
  *
- * @param fontCss - CSS string containing @font-face rules and/or @import statements
+ * @param fontCss - CSS string containing `@font-face` rules and/or `@import` statements
  *
  * @example Apply fonts from host context
  * ```typescript