fix: address review findings in sell KRK widget

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

web-app/src/components/LocalSwapWidget.vue

@@ -37,7 +37,7 @@
             <span class="swap-balance">Balance: {{ formattedKrkBalance }} KRK</span>
           </div>
           <div class="swap-input-row">
-            <input id="local-sell-amount" data-testid="swap-sell-amount-input" :value="sellAmount" @input="sellAmount = ($event.target as HTMLInputElement).value" type="number" min="0" step="1" class="swap-input" :disabled="selling" />
+            <input id="local-sell-amount" data-testid="swap-sell-amount-input" :value="sellAmount" @input="sellAmount = ($event.target as HTMLInputElement).value" type="number" min="0" step="0.01" class="swap-input" :disabled="selling" />
             <button class="max-button" :disabled="selling" @click="setMax">Max</button>
           </div>
         </div>
@@ -60,8 +60,11 @@ const { swapAmount, swapping, canSwap, buyKrk, sellAmount, selling, sellPhase, k
 const mode = ref<'buy' | 'sell'>('buy');
 
 const formattedKrkBalance = computed(() => {
-  const val = Number(formatUnits(krkBalance.value, 18));
-  return val.toLocaleString(undefined, { maximumFractionDigits: 4 });
+  const s = formatUnits(krkBalance.value, 18);
+  const [whole, frac = ''] = s.split('.');
+  const truncFrac = frac.slice(0, 4).replace(/0+$/, '');
+  const wholeFormatted = BigInt(whole).toLocaleString();
+  return truncFrac ? `${wholeFormatted}.${truncFrac}` : wholeFormatted;
 });
 
 function setMode(m: 'buy' | 'sell') {
@@ -69,7 +72,8 @@ function setMode(m: 'buy' | 'sell') {
   if (m === 'sell') loadKrkBalance();
 }
 
-function setMax() {
+async function setMax() {
+  await loadKrkBalance();
   sellAmount.value = formatUnits(krkBalance.value, 18);
 }
 

web-app/src/composables/useSwapKrk.ts

@@ -16,13 +16,6 @@ export const WETH_ABI = [
     stateMutability: 'payable',
     type: 'function',
   },
-  {
-    inputs: [{ internalType: 'uint256', name: 'wad', type: 'uint256' }],
-    name: 'withdraw',
-    outputs: [],
-    stateMutability: 'nonpayable',
-    type: 'function',
-  },
 ] as const satisfies Abi;
 
 export const SWAP_ROUTER_ABI = [
@@ -130,7 +123,7 @@ export function useSwapKrk() {
         chainId: resolvedChainId.value,
       });
     } catch {
-      krkBalance.value = 0n;
+      // Do not overwrite a previously loaded non-zero balance on RPC error
     }
   }
 
@@ -286,6 +279,35 @@ export function useSwapKrk() {
       });
       if (amount > balance) throw new Error('Insufficient KRK balance');
 
+      const factoryAddress = await readContract(wagmiConfig, {
+        abi: SWAP_ROUTER_ABI,
+        address: router,
+        functionName: 'factory',
+        chainId: currentChainId,
+      });
+      const factory = ensureAddress(factoryAddress, 'Uniswap factory');
+
+      const poolAddress = await readContract(wagmiConfig, {
+        abi: UNISWAP_FACTORY_ABI,
+        address: factory,
+        functionName: 'getPool',
+        args: [weth, harb, 10_000],
+        chainId: currentChainId,
+      });
+      if (!poolAddress || poolAddress === zeroAddress) {
+        throw new Error('No KRK/WETH pool found at 1% fee; deploy and recenter first');
+      }
+
+      const poolLiquidity = await readContract(wagmiConfig, {
+        abi: UNISWAP_POOL_ABI,
+        address: poolAddress,
+        functionName: 'liquidity',
+        chainId: currentChainId,
+      });
+      if (poolLiquidity === 0n) {
+        throw new Error('KRK/WETH pool has zero liquidity; run recenter before swapping');
+      }
+
       sellPhase.value = 'approving';
       const allowance = await readContract(wagmiConfig, {
         abi: erc20Abi,
@@ -325,12 +347,14 @@ export function useSwapKrk() {
 
       await loadBalance();
       await loadKrkBalance();
+      sellAmount.value = '';
 
       toast.success('Sell complete. WETH has been added to your wallet.');
     } catch (error: unknown) {
       toast.error(getErrorMessage(error, 'Sell failed'));
     } finally {
       selling.value = false;
+      sellPhase.value = 'approving';
     }
   }