chore(frontend): scrub pre-existing issue-tag refs from source comments

The no-issue-tags-in-code rule (knowledge/hive-rules.md) was enforced on
recent PRs but several pre-existing parenthetical refs remained in the
frontend source. Replace them with plain prose — issue numbers are opaque
in source, and prose survives repo migrations + doesn't confuse static
analysis. Comment-only; no behaviour change.

- tabs.js: 4× operator-inbox refs → prose
- flow.js / flow.css: agent-filter + sent/delivered-collapse refs → prose
- home.js / home.css: H0M3 page-script + page-chrome refs → prose
- dashboard.html: 1NB0X inbox ref → prose

Closes #1549.

frontend/packages/dashboard/src/dashboard.html

@@ -118,7 +118,7 @@
          can decide without leaving the pane. -->
     <section class="tab-pane" id="tab-pane-call" data-tab-pane="call" hidden
              role="tabpanel" aria-labelledby="tab-call">
-      <!-- 1NB0X: unread agent→operator messages (#1469). Fetched on
+      <!-- 1NB0X: unread agent→operator messages. Fetched on
            tab activation + cold load, appended live from the broker
            stream, cleared via "mark all read". Count folds into the
            Y3R C4LL pill so messages aren't missed. -->