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/types/note.ts

@@ -29,7 +29,7 @@ export interface Note {
   due_date: string | null;
   started_at: string | null;
   completed_at: string | null;
-  // Which session is working this task now (milestone 381). Null when no
+  // Which session is working this task now. Null when no
   // session ever claimed it; `live` false when the claim's lease ran out —
   // a session that went quiet mid-task, which is worth seeing, not hiding.
   claim?: TaskClaim | null;
@@ -38,7 +38,7 @@ export interface Note {
   is_task: boolean;
   note_type: NoteType;
   task_kind?: TaskKind;
-  // The note's own check (milestone 317). Empty on almost every note — that
+  // The note's own check. Empty on almost every note — that
   // is the normal case: a note with no `verify_with` is a DECISION, and there
   // is nothing to go and check. Only a note asserting a fact about something
   // outside the operator's control carries one. `verified_at` null while

frontend/src/types/usage.ts

@@ -5,7 +5,7 @@
  * One shape for every record kind the retrieval surfaces can choose. Snippets
  * and notes are counted in `note_usage_events`; rules in `rule_usage_events`,
  * which is a separate table because a note id and a rule id are different
- * namespaces resolved through different maps at restore (milestone 333). The
+ * namespaces resolved through different maps at restore. The
  * TABLES are separate for that reason; the READOUT is the same question, so
  * the client type is one.
  *
@@ -21,7 +21,7 @@ export interface RecordUsage {
   last_surfaced_at: string | null;
   last_pulled_at: string | null;
   /** The subsets that happened on a project other than the record's own —
-   *  the evidence it transferred (milestone 385). Notes and snippets carry
+   *  the evidence it transferred. Notes and snippets carry
    *  them; rules are global, so their readout does not. */
   surfaced_away_count?: number;
   pulled_away_count?: number;