fix(governance): countersign only the committed unit and a near-present event time

countersign_fulfillment is an unrestricted grant, so the non-author could
call it directly to collect the author's signature over any unit or a
backdated time. It now refuses an observed unit that differs from the
committed one and an event time more than five minutes from its clock.
The event form's empty quantity falls back to 1 as intended (an empty
number input binds null).

Author: Soushi888

dnas/nondominium/zomes/coordinator/zome_gouvernance/src/fulfillment.rs

@@ -606,6 +606,31 @@ pub fn countersign_fulfillment(
       "countersign_fulfillment: invalid observed_quantity: {e}"
     )))
   })?;
+  // What I committed to bounds what I countersign: the observed quantity
+  // keeps the committed unit, and the event time is close to my own clock,
+  // so a direct call cannot collect my signature for another unit or a
+  // backdated event.
+  if let Some(committed) = &commitment.resource_quantity {
+    if committed.has_unit != input.observed_quantity.has_unit {
+      return Err(
+        GovernanceError::InvalidInput(format!(
+          "countersign_fulfillment: observed unit {:?} differs from the committed unit {:?}",
+          input.observed_quantity.has_unit, committed.has_unit
+        ))
+        .into(),
+      );
+    }
+  }
+  let my_now = sys_time()?.as_micros();
+  let skew = (my_now - input.event_time.as_micros()).abs();
+  if skew > COUNTERSIGN_MAX_CLOCK_SKEW_MICROS {
+    return Err(
+      GovernanceError::InvalidInput(
+        "countersign_fulfillment: event time is too far from my clock".to_string(),
+      )
+      .into(),
+    );
+  }
 
   // Rebuild the payload from what I can see (the commitment I fetched, the
   // observed quantity and the event time) and sign my own hash, never the
@@ -727,6 +752,9 @@ fn build_fulfillment_signing_data(
   data
 }
 
+/// How far the initiator's event time may be from the countersigner's clock.
+const COUNTERSIGN_MAX_CLOCK_SKEW_MICROS: i64 = 5 * 60 * 1_000_000;
+
 fn blake3_hash(data: &[u8]) -> [u8; 32] {
   let mut hasher = Hasher::new();
   hasher.update(data);

ui/src/lib/components/ndo/EconomicEventCreateForm.svelte

@@ -158,7 +158,10 @@
         resource_inventoried_as: resource,
         resource_quantity: {
           // A Measure may be 0; only a missing or non-numeric value falls back to 1.
-          numerical_value: Number.isFinite(Number(quantity)) && String(quantity) !== '' ? Number(quantity) : 1,
+          numerical_value:
+            quantity == null || String(quantity).trim() === '' || !Number.isFinite(Number(quantity))
+              ? 1
+              : Number(quantity),
           has_unit: unit.trim() || 'each'
         },
         note: note.trim() || null,