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/router/index.ts

@@ -72,8 +72,8 @@ const router = createRouter({
     {
       // Lessons have no list view of their own: the Knowledge browse surface
       // is where every kind is enumerated, and a second list would be a
-      // second vocabulary to keep in step with it (#3128's defect, in
-      // advance). `/knowledge?type=lesson` is the list.
+      // second vocabulary to keep in step with it. `/knowledge?type=lesson` is
+      // the list.
       path: "/lessons/new",
       name: "lesson-new",
       component: () => import("@/views/LessonEditorView.vue"),
@@ -129,7 +129,7 @@ const router = createRouter({
       component: () => import("@/views/RulesView.vue"),
     },
     {
-      // Family canon (milestone 463): ideas shared across every project on a
+      // Family canon: ideas shared across every project on a
       // platform, and the log of every decision about them.
       path: "/family",
       name: "family",