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.

docs/CURRENT-STATE.md

@@ -4239,6 +4239,10 @@ by `scripts/qa-emergency-squawk.mjs`. Both accept `--timeout-ms` for slow boot.
 
 Fire Perimeters uses capped, timed server reads with stale-on-error caching and a per-client limit. A stale snapshot is served for at most 24 hours; the layer row then reads STALE, dated by that snapshot's fetch, and `get_fire_perimeters` returns `stale` and `retrieved_at` with "(data may be stale)" in its summary. Unchanged snapshots retain geometry; link checks cancel on disable or selection change, and the row legend shows reported containment.
 
+The incident card rounds the WFIGS size to whole acres, except under one acre,
+where it keeps the reported hundredths: a 0.25-acre fire reads `0.25 ac`, not
+`0 ac`.
+
 Prohibited & Restricted Airspace is off by default (share-link token `8`) and sits in
 Infrastructure. The proxy pages `TYPE_CODE IN ('P','R')` from the FAA SUA
 FeatureServer, caps the body, and reuses a one-hour snapshot, serving the last