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/assets/moments-shared.css

@@ -1,4 +1,4 @@
-/* Moments (milestone 458): the pieces the rule editor's picker and the
+/* Moments: the pieces the rule editor's picker and the
    Settings section share, so a moment's name and a chip's remove control look
    the same wherever a person meets them. Loaded unscoped by both. */
 

frontend/src/assets/rules-shared.css

@@ -20,8 +20,8 @@
    milestone (tier, then verification) and were byte-identical; a third would
    have drifted. The pane's italic serif title is inherited by anything inside
    it, so the chip resets family and style explicitly. */
-/* A rule with no trigger cannot be retrieved, and since milestone 394
-   retrieval is the only delivery — so this marks a rule that will never
+/* A rule with no trigger cannot be retrieved, and retrieval is the only
+   delivery — so this marks a rule that will never
    reach a session. Warning rather than error: the rule is not broken, it is
    unreachable, and the fix is one field away. */
 .rule-chip-inert {

frontend/src/assets/theme.css

@@ -208,11 +208,8 @@
  */
 
 /* ==========================================================================
-   The compatibility-alias block that lived here is GONE (#2533). It let ~55
-   components keep their historical --color-* names while theme.css was
-   repointed at the design system; the rename sweep it promised ran on
-   2026-08-08 and every component now references --fs-* directly. Do not
-   reintroduce app-local alias names — the design system's tokens are the
+   Every component references the design system's --fs-* tokens directly.
+   Do not introduce app-local alias names — the design system's tokens are the
    vocabulary, and check_snippets_against_design_system can only see through
    names the system actually declares.
    ========================================================================== */