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/flow.css

@@ -88,7 +88,7 @@ body.flow-shell .flow-main-slim {
   padding: 0.4em 1em;
 }
 
-/* Agent filter (#1473): a select in the FL0W header narrows the
+/* Agent filter: a select in the FL0W header narrows the
    timeline to messages involving one agent. Non-matching rows get
    `.flow-hidden`; the select reuses the journal-unit control look. */
 .flow-filter {