SUNDIAL solar dial v0.3: round screen, NOAA solar math, day/night arc

- 466px round layout, designWidth 466 (S4 41mm 466x466)
- solar position + dayProgress in src/common/solar.js (pure, TDD'd)
- sunrise/sunset sweep, night moon, countdown, 30s refresh
- tests: solar math, page logic, circle geometry/contrast

src/common/icon.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="192" height="192" viewBox="0 0 192 192">
+  <rect width="192" height="192" rx="48" fill="#ff6900"/>
+  <text x="96" y="116" text-anchor="middle" font-family="DejaVu Sans, sans-serif" font-size="72" font-weight="700" fill="#ffffff">Hi</text>
+</svg>

src/common/solar.js

@@ -0,0 +1,91 @@
+// Solar position — NOAA solar calculator algorithm (Astronomical Algorithms, Meeus).
+// All functions pure; no Vela APIs. Exports: solarPosition, dayProgress, formatCountdown.
+const RAD = Math.PI / 180
+const DEG = 180 / Math.PI
+
+function julianDay(date) {
+  return date.getTime() / 86400000 + 2440587.5
+}
+
+function sunVector(date) {
+  const jd = julianDay(date)
+  const n = jd - 2451545.0
+  const L = (280.460 + 0.9856474 * n) % 360        // mean longitude
+  const g = ((357.528 + 0.9856003 * n) % 360) * RAD // mean anomaly
+  const lambda = (L + 1.915 * Math.sin(g) + 0.020 * Math.sin(2 * g)) * RAD // ecliptic longitude
+  const eps = (23.439 - 0.0000004 * n) * RAD        // obliquity
+  const declination = Math.asin(Math.sin(eps) * Math.sin(lambda)) * DEG
+  const rightAscension = Math.atan2(Math.cos(eps) * Math.sin(lambda), Math.cos(lambda)) * DEG
+  const gmst = (18.697374558 + 24.06570982441908 * n) % 24 // sidereal hours
+  return { declination, rightAscension: (rightAscension + 360) % 360, gmst: (gmst + 24) % 24 }
+}
+
+// altitude/azimuth in degrees; azimuth 0=N, 90=E
+function solarPosition(date, latDeg, lonDeg) {
+  const { declination, rightAscension, gmst } = sunVector(date)
+  const lat = latDeg * RAD
+  const hourAngle = ((gmst * 15 + lonDeg - rightAscension + 180) % 360 - 180) * RAD
+  const sinAlt = Math.sin(lat) * Math.sin(declination * RAD) + Math.cos(lat) * Math.cos(declination * RAD) * Math.cos(hourAngle)
+  const altitude = Math.asin(Math.max(-1, Math.min(1, sinAlt))) * DEG
+  const az = Math.atan2(
+    -Math.sin(hourAngle),
+    Math.tan(lat) * Math.cos(declination * RAD) - Math.sin(declination * RAD) * Math.cos(hourAngle)
+  ) * DEG
+  return { altitude, azimuth: (az + 360) % 360 }
+}
+
+// fraction of daylight elapsed at `date` (0 sunrise → 1 sunset; 0 before, 1 after)
+function dayProgress(date, latDeg, lonDeg) {
+  // scan the last 48h for the latest crossing at or before `date`
+  let lastSunrise = NaN, lastSunset = NaN
+  for (let h = 1; h <= 48; h++) {
+    const t = date.getTime() - h * 3600e3
+    const altT = solarPosition(new Date(t), latDeg, lonDeg).altitude
+    const altNext = solarPosition(new Date(t + 3600e3), latDeg, lonDeg).altitude
+    if (altT <= 0 && altNext > 0) { lastSunrise = t; break }
+  }
+  for (let h = 1; h <= 48; h++) {
+    const t = date.getTime() - h * 3600e3
+    const altT = solarPosition(new Date(t), latDeg, lonDeg).altitude
+    const altNext = solarPosition(new Date(t + 3600e3), latDeg, lonDeg).altitude
+    if (altT > 0 && altNext <= 0) { lastSunset = t; break }
+  }
+  // next sunset (forward scan)
+  let nextSunset = NaN
+  for (let h = 1; h <= 48; h++) {
+    const t = date.getTime() + h * 3600e3
+    const altT = solarPosition(new Date(t), latDeg, lonDeg).altitude
+    const altNext = solarPosition(new Date(t + 3600e3), latDeg, lonDeg).altitude
+    if (altT > 0 && altNext <= 0) { nextSunset = t + 3600e3; break }
+  }
+  if (Number.isNaN(lastSunrise)) return 0 // no sunrise in 48h → polar night
+  // find next sunrise (forward scan) to disambiguate late-evening vs pre-dawn night
+  let nextSunrise = NaN
+  for (let h = 1; h <= 48; h++) {
+    const t = date.getTime() + h * 3600e3
+    const altT = solarPosition(new Date(t), latDeg, lonDeg).altitude
+    const altNext = solarPosition(new Date(t + 3600e3), latDeg, lonDeg).altitude
+    if (altT <= 0 && altNext > 0) { nextSunrise = t + 3600e3; break }
+  }
+  // night: past sunset (→1) until solar midnight, then pre-dawn (→0)
+  if (!Number.isNaN(lastSunset) && lastSunset > lastSunrise) {
+    if (Number.isNaN(nextSunrise)) return 1 // midnight sun edge
+    const solarMidnight = lastSunset + (nextSunrise - lastSunset) / 2
+    return date.getTime() < solarMidnight ? 1 : 0
+  }
+  if (Number.isNaN(nextSunset)) return 1 // midnight sun
+  const span = nextSunset - lastSunrise
+  if (span <= 0) return 1
+  return Math.max(0, Math.min(1, (date.getTime() - lastSunrise) / span))
+}
+
+function formatCountdown(seconds) {
+  const s = Math.max(0, Math.round(seconds))
+  if (s === 0) return '0m'
+  if (s < 60) return '<1m'
+  const m = Math.round(s / 60)
+  if (m < 60) return m + 'm'
+  return Math.floor(m / 60) + 'h ' + (m % 60) + 'm'
+}
+
+module.exports = { solarPosition, dayProgress, formatCountdown }