feat: pace chart and spm cadence for running/hiking/walking/other

Speed tab becomes Pace tab (min/km, y-axis inverted so faster = top).
Cadence label switches to spm. Tooltip and reference lines use m:ss format.

site/src/components/ActivityCharts.svelte

@@ -1,13 +1,24 @@
 <script lang="ts">
   import * as Plot from '@observablehq/plot';
   import { onMount, onDestroy } from 'svelte';
-  import type { Timeseries, AthleteZones } from '../lib/types';
+  import type { Timeseries, AthleteZones, Sport } from '../lib/types';
+  import { isPaceSport } from '../lib/format';
 
   export let timeseries: Timeseries;
+  export let sport: string = 'cycling';
   // Linked hover: emit/receive index into timeseries arrays
   export let hoveredIdx: number | null = null;
   export let athlete: AthleteZones | null = null;
 
+  $: isPace = isPaceSport(sport as Sport);
+
+  function fmtPaceValue(v: number | null): string {
+    if (v == null || v <= 0) return '—';
+    const m = Math.floor(v);
+    const s = Math.round((v - m) * 60);
+    return `${m}:${String(s).padStart(2, '0')}`;
+  }
+
   const HR_ZONE_COLORS  = ['#60a5fa', '#4ade80', '#facc15', '#fb923c', '#f87171'];
   const PWR_ZONE_COLORS = ['#60a5fa', '#34d399', '#facc15', '#fb923c', '#f87171', '#c084fc', '#f43f5e'];
 
@@ -43,15 +54,19 @@
   })();
 
   // Pre-build data array once
-  $: data = timeseries.t.map((t, i) => ({
+  $: data = timeseries.t.map((t, i) => {
+    const spd = timeseries.speed_kmh[i];
+    return {
       t,
       dist_km: dist_km ? dist_km[i] : null,
       elevation: timeseries.elevation_m[i],
-    speed: timeseries.speed_kmh[i],
+      speed: spd,
+      pace: (spd != null && spd > 0) ? 60 / spd : null,
       hr: timeseries.hr_bpm[i],
       cadence: timeseries.cadence_rpm[i],
       power: timeseries.power_w[i],
-  }));
+    };
+  });
 
   $: hasHR        = timeseries.hr_bpm.some(v => v != null);
   $: hasCadence   = timeseries.cadence_rpm.some(v => v != null);
@@ -61,23 +76,23 @@
   $: hasDistance  = dist_km !== null;
   $: hasSlope     = hasElevation && hasDistance;
 
-  const tabLabels: Record<Tab, string> = {
+  $: tabLabels = {
     elevation: 'Elevation',
     slope:     'Slope',
-    speed:     'Speed',
+    speed:     isPace ? 'Pace' : 'Speed',
     hr:        'Heart Rate',
     cadence:   'Cadence',
     power:     'Power',
-  };
+  } as Record<Tab, string>;
 
-  const tabMeta: Record<Tab, { color: string; yLabel: string; yKey: string }> = {
+  $: tabMeta = {
     elevation: { color: '#00c8ff', yLabel: 'Elevation (m)',                          yKey: 'elevation' },
     slope:     { color: '#e4e4e7', yLabel: 'Elevation (m)',                          yKey: 'elevation' },
-    speed:     { color: '#ff6b35', yLabel: 'Speed (km/h)',     yKey: 'speed'     },
+    speed:     { color: '#ff6b35', yLabel: isPace ? 'Pace (min/km)' : 'Speed (km/h)', yKey: isPace ? 'pace' : 'speed' },
     hr:        { color: '#f87171', yLabel: 'Heart Rate (bpm)',                       yKey: 'hr'        },
-    cadence:   { color: '#a78bfa', yLabel: 'Cadence (rpm)',    yKey: 'cadence'   },
+    cadence:   { color: '#a78bfa', yLabel: isPace ? 'Cadence (spm)' : 'Cadence (rpm)', yKey: 'cadence' },
     power:     { color: '#facc15', yLabel: 'Power (W)',                              yKey: 'power'     },
-  };
+  } as Record<Tab, { color: string; yLabel: string; yKey: string }>;
 
   // ── Histogram controls ───────────────────────────────────────────────────
   let bins = 15;
@@ -96,7 +111,7 @@
   // Plot auto-infers different domains when the x-channel changes because it only
   // considers plottable points, but we want the scale to stay anchored to the
   // full dataset.  areaY extends down to 0, so include 0 in the minimum.
-  $: lineDomainMin = Math.min(0, dataMin);
+  $: lineDomainMin = (activeTab === 'speed' && isPace) ? dataMin : Math.min(0, dataMin);
   $: lineDomainMax = dataMax;
 
   // Range handles — reset whenever the metric or chart type changes
@@ -335,9 +350,9 @@
         Plot.ruleY([ref.p20, ref.p80], { stroke: tc.axis, strokeWidth: 1, strokeDasharray: '3,4', strokeOpacity: 0.55 }),
         Plot.text(
           [
-            { xv: xEnd, yv: ref.avg, label: `avg ${Math.round(ref.avg)}` },
-            { xv: xEnd, yv: ref.p20, label: `P20 ${Math.round(ref.p20)}` },
-            { xv: xEnd, yv: ref.p80, label: `P80 ${Math.round(ref.p80)}` },
+            { xv: xEnd, yv: ref.avg, label: activeTab === 'speed' && isPace ? `avg ${fmtPaceValue(ref.avg)}` : `avg ${Math.round(ref.avg)}` },
+            { xv: xEnd, yv: ref.p20, label: activeTab === 'speed' && isPace ? `P20 ${fmtPaceValue(ref.p20)}` : `P20 ${Math.round(ref.p20)}` },
+            { xv: xEnd, yv: ref.p80, label: activeTab === 'speed' && isPace ? `P80 ${fmtPaceValue(ref.p80)}` : `P80 ${Math.round(ref.p80)}` },
           ],
           { x: 'xv', y: 'yv', text: 'label', textAnchor: 'end', dx: -4, dy: -6,
             fill: tc.tooltipFg, stroke: tc.tooltipBg, strokeWidth: 3, fontSize: 11 },
@@ -376,7 +391,11 @@
       marks.push(
         Plot.text(lineData, Plot.pointerX({
           x, y: yKey,
-          text: (d: any) => d[yKey] != null ? `${Math.round(d[yKey])}` : '',
+          text: (d: any) => {
+            const v = d[yKey];
+            if (v == null) return '';
+            return (activeTab === 'speed' && isPace) ? fmtPaceValue(v) : `${Math.round(v)}`;
+          },
           dy: -12,
           fill: tc.tooltipFg, stroke: tc.tooltipBg, strokeWidth: 3,
           fontSize: 11, fontWeight: '600',
@@ -396,7 +415,11 @@
       width: w, height: h, marginLeft: 48, marginBottom: 32, marginTop: isSlope ? 36 : 20,
       style: { background: 'transparent', color: tc.axis, fontSize: '11px' },
       x: { label: null, tickFormat: xTickFormat, grid: false, ticks: 6 },
-      y: { label: yLabel, grid: true, tickCount: 4, domain: [lineDomainMin, lineDomainMax] },
+      y: {
+        label: yLabel, grid: true, tickCount: 4,
+        domain: (activeTab === 'speed' && isPace) ? [lineDomainMax, lineDomainMin] : [lineDomainMin, lineDomainMax],
+        tickFormat: (activeTab === 'speed' && isPace) ? (v: number) => fmtPaceValue(v) : undefined,
+      },
       marks,
     });
 
@@ -488,7 +511,8 @@
     return Plot.plot({
       width: w, height: h, marginLeft: 48, marginBottom: 32,
       style: { background: 'transparent', color: tc.axis, fontSize: '11px' },
-      x: { label: yLabel, grid: false, ticks: 6, domain: [trimMin, trimMax] },
+      x: { label: yLabel, grid: false, ticks: 6, domain: [trimMin, trimMax],
+           tickFormat: (activeTab === 'speed' && isPace) ? (v: number) => fmtPaceValue(v) : undefined },
       y: { label: 'Time', grid: true, tickCount: 4, tickFormat: yTickFormat },
       marks,
     });

site/src/components/ActivityDetail.svelte

@@ -445,7 +445,7 @@
       <p class="text-red-400 text-sm">{error}</p>
     {:else if timeseries && timeseries.t.length > 0}
       <div class="bg-zinc-900 rounded-xl border border-zinc-800 p-4">
-        <ActivityCharts {timeseries} bind:hoveredIdx {athlete} />
+        <ActivityCharts {timeseries} sport={activity.sport} bind:hoveredIdx {athlete} />
       </div>
     {:else if !detail || timeseriesLoading}
       <div class="bg-zinc-900 rounded-xl border border-zinc-800 p-4 h-32 animate-pulse"></div>