Fix code highlighting and optimize category select

This commit introduces a batched debounce mechanism for managing user
selection state changes. It effectively reduces unnecessary processing
during rapid script checking, preventing multiple triggers for code
compilation and UI rendering.

Key improvements include:

- Enhanced performance, especially noticeable when selecting large
  categories. This update resolves minor UI freezes experienced when
  selecting categories with numerous scripts.
- Correction of a bug where the code area only highlighted the last
  selected script when multiple scripts were chosen.

Other changes include:

- Timing functions:
  - Create a `Timing` folder for `throttle` and the new
    `batchedDebounce` functions.
  - Move these functions to the application layer from the presentation
    layer, reflecting their application-wide use.
  - Refactor existing code for improved clarity, naming consistency, and
    adherence to new naming conventions.
  - Add missing unit tests.
- `UserSelection`:
  - State modifications in `UserSelection` now utilize a singular object
    inspired by the CQRS pattern, enabling batch updates and flexible
    change configurations, thereby simplifying change management.
- Remove the `I` prefix from related interfaces to align with new coding
  standards.
- Refactor related code for better testability in isolation with
  dependency injection.
- Repository:
  - Move repository abstractions to the application layer.
  - Improve repository abstraction to combine `ReadonlyRepository` and
    `MutableRepository` interfaces.
- E2E testing:
  - Introduce E2E tests to validate the correct batch selection
    behavior.
  - Add a specialized data attribute in `TheCodeArea.vue` for improved
    testability.
  - Reorganize shared Cypress functions for a more idiomatic Cypress
    approach.
  - Improve test documentation with related information.
- `SelectedScript`:
  - Create an abstraction for simplified testability.
  - Introduce `SelectedScriptStub` in tests as a substitute for the
    actual object.

tests/e2e/card-list-layout-stability-on-load.cy.ts

@@ -1,5 +1,5 @@
 // eslint-disable-next-line max-classes-per-file
-import { waitForHeaderBrandTitle } from './shared/ApplicationLoad';
+import { getHeaderBrandTitle } from './support/interactions/header';
 
 interface Stoppable {
   stop(): void;
@@ -175,7 +175,7 @@ enum ApplicationLoadStep {
 const checkpoints: Record<ApplicationLoadStep, () => void> = {
   [ApplicationLoadStep.IndexHtmlLoaded]: () => cy.get('#app').should('be.visible'),
   [ApplicationLoadStep.AppVueLoaded]: () => cy.get('.app__wrapper').should('be.visible'),
-  [ApplicationLoadStep.HeaderBrandTitleLoaded]: () => waitForHeaderBrandTitle(),
+  [ApplicationLoadStep.HeaderBrandTitleLoaded]: () => getHeaderBrandTitle(),
 };
 
 class ContinuousRunner implements Stoppable {