docs(6208): the remaining frontend comments drop milestone, step and rule citations

Components, stores, api clients, router, types and shared CSS now state what
each piece is and why, without the milestone that introduced it. diff.ts
names its consumers instead of the copy history; stores/notes and tasks state
their current scope instead of the cleanup that set it; theme.css states the
token practice instead of the sweep that established it.

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

frontend/src/api/inception.ts

@@ -1,11 +1,11 @@
-/** Project inception (milestone 297): what a project was decided to inherit. */
+/** Project inception: what a project was decided to inherit. */
 import { apiGet, apiPost } from "@/api/client";
 import type { ProjectPlatform } from "@/api/platforms";
 
 export interface InceptionChoices {
   design_system_id: number | null;
   seed_systems: boolean;
-  /** Platform slugs (milestone 463). null = not answered; a list is the
+  /** Platform slugs. null = not answered; a list is the
    *  whole answer — members left out of it are recorded as "not this".
    *  Absent on records decided before the question existed. */
   platforms?: string[] | null;