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/home.js

@@ -1,4 +1,4 @@
-// H0M3 page script (#1464). The page is static markup; this only does
+// H0M3 page script. The page is static markup; this only does
 // a few small things off a single `/api/state` read:
 //   1. reveal the Matrix tile when the matrix GUI is enabled (same
 //      gating as the dashboard's M4TR1X tab — no dead link otherwise);