Refresh legacy pages, align Seth rules text, and ship astronomy location controls

RELEASE_CONTEXT.md

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+# Seth Clock Suite - Major Refresh Context
+
+Date: 2026-03-09
+Scope: `clock.sethpc.xyz` static app suite
+
+## Highlights
+
+- Astronomy page now shows Seth/Gregorian columns for core metrics.
+- Astronomy event list now shows dual dates (Seth + Gregorian) per item.
+- Astronomy location controls added:
+  - manual lat/lon + label
+  - US ZIP lookup
+  - browser geolocation helper
+  - session persistence (`sessionStorage`) with cookie mirror fallback
+- Navigation consistency improved across pages (`/`, `/decimal`, `/convert`, `/seth`, `/calendar`, `/astro`).
+- Seth Date reference text corrected for auxiliary day rules and Dec 25/26 mappings.
+
+## Canonical Seth rules reflected
+
+- 10 months x 36 days (0-indexed)
+- Leap day is intercalary (outside month grid)
+- Auxiliary days are always H0-H4 (5 total)
+- Dec 25 -> M9D34, Dec 26 -> M9D35 (both leap and non-leap)
+
+## Operational notes
+
+- Repo path: `/root/bin/clock-site`
+- Live deployment path: CT 242 `/opt/clock-site`
+- Service: `clock.service`
+- Domain: `clock.sethpc.xyz`