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)

dashboard/pyproject.toml

@@ -0,0 +1,29 @@
+[project]
+name = "gpsntp-dashboard"
+version = "2026.07.12"
+description = "Live status dashboard for a GPS/PPS-disciplined chrony Stratum 1 time server"
+readme = "README.md"
+requires-python = ">=3.11"
+authors = [{name = "Ryan Malloy", email = "ryan@supported.systems"}]
+license = {text = "MIT"}
+dependencies = [
+    "fastapi>=0.115",
+    "uvicorn[standard]>=0.34",
+]
+
+[project.scripts]
+gpsntp-dashboard = "gpsntp_dashboard.main:run"
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/gpsntp_dashboard"]
+
+[tool.ruff]
+line-length = 100
+target-version = "py311"
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "UP", "B"]