fix(perimeters): show a 0.25-acre fire as 0.25 ac, not 0 ac

The incident card rounded the WFIGS size to whole acres, so every fire
under half an acre read "0 ac". The live perimeter feed carries many of
these (0.01 to 0.37 acres). Sizes under one acre now keep the reported
hundredths.

src/layers/perimeters/cards.js

@@ -159,7 +159,10 @@ export function buildIncidentCard(row, nowMs, { link = null } = {}) {
   // the known cause, behavior and complexity values and the wording around them.
   const facts = [];
   if (Number.isFinite(row.acres)) {
-    const acres = Math.round(row.acres);
+    // WFIGS reports sizes to the hundredth of an acre; a fire under one acre
+    // keeps them rather than reading "0 ac".
+    const acres =
+      row.acres < 1 ? Math.round(row.acres * 100) / 100 : Math.round(row.acres);
     facts.push(
       tn(acres, '{acres} ac', '{acres} ac', { acres: formatNumber(acres) }),
     );

src/layers/perimeters/cards.test.mjs

@@ -302,3 +302,34 @@ test('partial incident details render only the facts that exist', () => {
     'Catron County · $85K to date',
   ]);
 });
+
+test('a fire under one acre keeps its WFIGS size instead of reading 0 ac', () => {
+  const row = {
+    stableId: 'x',
+    name: 'Grey',
+    acres: 0.25,
+    containedPct: null,
+    state: 'US-WA',
+    category: 'WF',
+    discoveredTime: null,
+    updatedTime: null,
+    cause: null,
+    behavior: null,
+    personnel: null,
+    county: null,
+    costToDate: null,
+    complexity: null,
+  };
+  assert.equal(
+    buildIncidentCard(row, 1758000000000).details[0],
+    '0.25 ac · containment unknown · US-WA',
+  );
+  assert.equal(
+    buildIncidentCard({ ...row, acres: 0.01 }, 1758000000000).details[0],
+    '0.01 ac · containment unknown · US-WA',
+  );
+  assert.equal(
+    buildIncidentCard({ ...row, acres: 1.4 }, 1758000000000).details[0],
+    '1 ac · containment unknown · US-WA',
+  );
+});