docs - add service dependency declaration guideline (#305682)

* docs - add service dependency declaration guideline

* Update .github/copilot-instructions.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

.github/copilot-instructions.md

@@ -146,6 +146,7 @@ function f(x: number, y: string): void { }
 - Use `IEditorService` to open editors instead of `IEditorGroupsService.activeGroup.openEditor` to ensure that the editor opening logic is properly followed and to avoid bypassing important features such as `revealIfOpened` or `preserveFocus`.
 - Avoid using `bind()`, `call()` and `apply()` solely to control `this` or partially apply arguments; prefer arrow functions or closures to capture the necessary context, and use these methods only when required by an API or interoperability.
 - Avoid using events to drive control flow between components. Instead, prefer direct method calls or service interactions to ensure clearer dependencies and easier traceability of logic. Events should be reserved for broadcasting state changes or notifications rather than orchestrating behavior across components.
+- Service dependencies MUST be declared in constructors and MUST NOT be accessed through the `IInstantiationService` at any other point in time.
 
 ## Learnings
 - Minimize the amount of assertions in tests. Prefer one snapshot-style `assert.deepStrictEqual` over multiple precise assertions, as they are much more difficult to understand and to update.