feat(storm-intel): damage-probability homes estimate + pinned events total in header

useStormEvents:
- Replace flat 1800/sq mi estimate with damage probability multiplier per type:
  hail ≥2.0" = 95%, 1.75" = 80%, 1.5" = 65%, 1.25" = 45%, 1.0" = 30%, <1.0" = 15%;
  tornado = 20% (path << polygon), flood = 25%, wind = 40%, winter = 20-30%
- Expose damagePct on event object for display in drawer

StormIntelPage:
- pinnedHomes useMemo — sums estimatedHomes across event-pinned events
- Header homes stat switches to amber + "Est. Homes · N pinned" label when events are pinned;
  hover tooltip notes zones may overlap
- Drawer: "Est. Homes Affected" now shows "~X% damage probability" as sub-label

src/hooks/useStormEvents.js

@@ -111,9 +111,7 @@ function featureToEvent(feature, idx) {
         ? Math.round((new Date(expireTime) - new Date(issueTime)) / 60000)
         : null;
 
-    const areaSqMi     = Math.round(polygonAreaSqMi(polygon));
-    // Suburban DFW density ~1 800 homes/sq mi — conservative (polygons often include open land)
-    const estHomes     = Math.round(areaSqMi * 1800);
+    const areaSqMi = Math.round(polygonAreaSqMi(polygon));
 
     const type = ph === 'TO'                        ? 'tornado'
                : ph === 'FF'                        ? 'flood'
@@ -128,6 +126,25 @@ function featureToEvent(feature, idx) {
         : ph === 'FF'   ? 'moderate'
         : 'significant';
 
+    // Damage probability: fraction of homes in the warning zone likely to have claimable damage.
+    // Tornado path is far narrower than the warning polygon, so we discount heavily.
+    // Hail probability scales with hail size — golf ball (2"+) damages nearly everything it hits.
+    const damagePct =
+          ph === 'TO'                  ? 20
+        : ph === 'FF'                  ? 25
+        : ph === 'WS' || ph === 'BZ'  ? 30
+        : ph === 'WW' || ph === 'IS'  ? 20
+        : hailIn === null              ? 40   // SV wind only
+        : hailIn >= 2.0                ? 95
+        : hailIn >= 1.75               ? 80
+        : hailIn >= 1.5                ? 65
+        : hailIn >= 1.25               ? 45
+        : hailIn >= 1.0                ? 30
+        :                                15;  // <1" — cosmetic, rarely claimed
+
+    // Homes in zone × suburban DFW density (1 800/sq mi) × damage probability
+    const estHomes = Math.round(areaSqMi * 1800 * (damagePct / 100));
+
     return {
         id:                   `IEM-${WFO}-${ph}-${p.year ?? ''}-${p.eventid ?? idx}`,
         date:                 issueTime || new Date().toISOString(),
@@ -142,6 +159,7 @@ function featureToEvent(feature, idx) {
         areaName:             derivedAreaName(rawCoords, ph),
         county:               'Collin',
         areaSqMi,
+        damagePct,
         estimatedHomes:       estHomes > 0 ? estHomes : null,
         description:          `${PH_LABEL[ph] ?? ph} — NWS ${WFO}`,
         source:               'IEM/NWS',