The Cuckoo Escapement: field report, kernel patch, dashboard

What the Raspberry Pi time-server guides get wrong on a Pi 4, with the
measurements. The headline artifact is a four-line pps-gpio patch: PREEMPT_RT
force-threads IRQ handlers, and pps-gpio takes its timestamp inside its handler,
so the realtime kernel puts a scheduler between the electrical edge and the
clock. IRQF_NO_THREAD takes RMS offset from 2468 ns to 199 ns.

- kernel/     the patch
- dashboard/  live status page (position hidden by default)
- docs-site/  the write-up (Astro/Starlight, brass, no tutorial section)

docs-site/src/components/Footer.astro

@@ -0,0 +1,13 @@
+---
+// Starlight Footer override. We wrap <Default /> so all upstream behavior —
+// last-updated stamp, prev/next pagination — is preserved, then append the
+// maker's plate below it.
+//
+// Same pattern (Default + extension) used across the other warehack.ing sites,
+// which keeps Starlight upgrades cheap.
+import Default from "@astrojs/starlight/components/Footer.astro";
+import SupportedSystemsBadge from "./SupportedSystemsBadge.astro";
+---
+
+<Default><slot /></Default>
+<SupportedSystemsBadge />

docs-site/src/components/SupportedSystemsBadge.astro

@@ -0,0 +1,47 @@
+---
+// "A Supported Systems Joint" — the maker's plate.
+//
+// Clockmakers signed the BACKPLATE: the flat brass face of the movement that
+// only shows when you open the case. It's the part a repairer sees a century
+// later, not the part the owner looks at. A site footer is the same thing —
+// the back of the movement — so this is an engraved plate rather than a
+// marketing strip, and nothing on it moves. A signature should be quiet.
+//
+// Shared verbatim with the dashboard's footer (static HTML/CSS port, same
+// markup and class names). Styles live in src/styles/brass.css.
+---
+
+<aside class="ss-plate" aria-label="Supported Systems">
+  <a class="ss-plate__link" href="https://supported.systems" rel="noopener">
+    <img
+      class="ss-plate__logo"
+      src="/supported-systems-logo.svg"
+      alt=""
+      width="52"
+      height="39"
+      loading="lazy"
+    />
+
+    <span class="ss-plate__copy">
+      <span class="ss-plate__heading">A Supported Systems Joint</span>
+      <span class="ss-plate__body">
+        The Cuckoo Escapement is built and maintained by
+        <span class="ss-plate__name">Supported Systems</span> &mdash; a boutique
+        software studio focused on thoughtful, user-first technology. We measure
+        things before we believe them.
+      </span>
+      <span class="ss-plate__cta">
+        Visit supported.systems
+        <svg viewBox="0 0 16 16" width="14" height="14" aria-hidden="true">
+          <path
+            d="M4 8h7M8 5l3 3-3 3"
+            fill="none"
+            stroke="currentColor"
+            stroke-width="1.5"
+            stroke-linecap="round"
+            stroke-linejoin="round"></path>
+        </svg>
+      </span>
+    </span>
+  </a>
+</aside>