dashy-soc-board: drop inaccurate cross-reference to architecture-overview.md

The 6-tier dependency ladder doesn't mirror that doc's trust-boundary
structure (4 boundaries, 3 routing authorities - a different taxonomy).
The 6-tier list only exists in the live code; no public doc documents
it, so the doc now describes it standalone instead of pointing at a
file that doesn't actually contain it.

docs/dashy-soc-board.md

@@ -35,7 +35,7 @@ Dashy's own built-in widget types cover simple cases well, but none of them can
 
 ## Layout
 
-A top row shows a 6-tier infrastructure dependency ladder (mirroring the trust-boundary structure in [`docs/architecture-overview.md`](architecture-overview.md)) alongside fleet-wide 24-hour KPIs. Below that, an "Active Issues" strip surfaces the worst findings fleet-wide, followed by a grid of per-host tiles — worst-severity badge, error sparkline, sorted consistently. Clicking a tile expands a full detail panel: compliance and resource gauges, that host's folded-in specialty widget where relevant (a Vault seal-state panel on the secrets host, a Wazuh compliance ring on any host, and so on), and findings grouped by category.
+A top row shows a 6-tier infrastructure dependency ladder alongside fleet-wide 24-hour KPIs. Below that, an "Active Issues" strip surfaces the worst findings fleet-wide, followed by a grid of per-host tiles — worst-severity badge, error sparkline, sorted consistently. Clicking a tile expands a full detail panel: compliance and resource gauges, that host's folded-in specialty widget where relevant (a Vault seal-state panel on the secrets host, a Wazuh compliance ring on any host, and so on), and findings grouped by category.
 
 This is the real board, not a mockup of the layout — the dependency ladder, the Wazuh 24h KPIs, the Active Issues strip (clean here — no critical/serious findings at the time this was captured), and the per-host tile grid with real sparklines and error counts: