fix: unstakePosition() has no error handling at all (#482)

Address AI reviewer warnings:
- Add separate unstakeError ref so unstake failures are not displayed
  via the load-data error UI whose Retry calls loadActivePositionData
- Add exitSucceeded flag to distinguish pre-exit failures ("Failed to
  unstake position.") from post-exit data-refresh failures ("Position
  unstaked, but failed to refresh data."), preventing factually wrong
  messages after a successful transaction
- Unstake error UI has no Retry button; the Unstake button in actions
  remains available for retrying a failed transaction

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web-app/src/components/collapse/CollapseActive.vue

@@ -39,6 +39,9 @@
         <span>{{ error }}</span>
         <FButton size="tiny" outlined @click="loadActivePositionData">Retry</FButton>
       </div>
+      <div v-if="unstakeError" class="collapsed-body--error">
+        <span>{{ unstakeError }}</span>
+      </div>
       <div v-if="!error || taxPaidGes !== undefined" class="profit-stats-wrapper">
         <div class="profit-stats-item">
           <div><b>Tax Cost</b></div>
@@ -122,6 +125,7 @@ const taxPaidGes = ref<number>();
 const profit = ref<number>();
 const loading = ref<boolean>(false);
 const error = ref<string | null>(null);
+const unstakeError = ref<string | null>(null);
 
 const tag = computed(() => {
   // Compare by index instead of decimal to avoid floating-point issues
@@ -214,9 +218,11 @@ async function changeTax(id: bigint, nextTaxRateIndex: number | null) {
 }
 
 async function unstakePosition() {
-  error.value = null;
+  unstakeError.value = null;
+  let exitSucceeded = false;
   try {
     await unstake.exitPosition(props.id);
+    exitSucceeded = true;
     loading.value = true;
     const POLL_INTERVAL_MS = 1000;
     const TIMEOUT_MS = 30_000;
@@ -230,8 +236,10 @@ async function unstakePosition() {
     await loadPositions(currentChainId.value);
   } catch (err) {
     // eslint-disable-next-line no-console
-    console.error('Failed to unstake position:', err);
-    error.value = 'Failed to unstake position.';
+    console.error(exitSucceeded ? 'Failed to refresh positions after unstake:' : 'Failed to unstake position:', err);
+    unstakeError.value = exitSucceeded
+      ? 'Position unstaked, but failed to refresh data.'
+      : 'Failed to unstake position.';
   } finally {
     loading.value = false;
   }