fix(settings): re-render OnPush sections when the form changes outside them

Review follow-ups (Greptile, Codex):

- The settings sections read form values in their templates (selected
  theme and cover size, epgField.value, form().value.player), and the
  parent changes the form outside their events: Discard and backup import
  patch it, the store hydrates it, the EPG file picker sets a control
  after an await. Under OnPush the section kept the old selection or EPG
  status. Each section now marks itself on its form's events
  (markSectionForCheckOnFormEvents).
- The value-only patch test no longer forces detectChanges(); with the
  fixture rendering on its own it fails without the marking, and so does
  a new test for a control set outside the EPG section.
- The zoneless guard counts only changeDetection metadata outside
  comments, so a comment naming the strategy is not an Eager component.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/architecture/zoneless-migration.md

@@ -63,7 +63,12 @@ must be ticked here.
 two). Tick an entry by deleting `changeDetection: ChangeDetectionStrategy.Eager`
 (or setting OnPush) once its template state is signals, signal inputs or
 explicitly marked. The guard spec compares the unticked entries with the
-files that still contain `ChangeDetectionStrategy.Eager`.
+files whose component metadata still sets
+`changeDetection: ChangeDetectionStrategy.Eager` (comments do not count).
+The settings sections read form values in their templates and the parent
+patches the form outside their events (Discard, backup import, the EPG file
+picker), so each marks itself on the form's `events` through
+`markSectionForCheckOnFormEvents` (`apps/web/src/app/settings`).
 
 ### apps/web (15)