feat(simple): add manage existing holding flow

web/src/views/SimpleView.tsx

@@ -667,6 +667,10 @@ export function SimpleView() {
     () => simpleHoldings.find((holding) => holding.symbol === normalizedSymbol) || null,
     [simpleHoldings, normalizedSymbol],
   );
+  const availableSellHoldings = useMemo(
+    () => [...simpleHoldings].sort((left, right) => left.symbol.localeCompare(right.symbol)),
+    [simpleHoldings],
+  );
 
   const supportedSymbols = useMemo(() => {
     const fromState = Object.keys(symbolState || {}).map(normalizeKnownSymbol).filter(Boolean) as string[];
@@ -751,6 +755,24 @@ export function SimpleView() {
     setDraft((prev) => ({ ...prev, [key]: value }));
   }
 
+  function applyHoldingToDraft(holding: SimpleHolding) {
+    setMarketPriceSource(null);
+    setDraft((prev) => ({
+      ...prev,
+      side: 'sell',
+      symbol: holding.symbol,
+      quantity: String(holding.size),
+      currentMarketPrice: '',
+    }));
+  }
+
+  useEffect(() => {
+    if (draft.side !== 'sell') return;
+    if (matchingHolding) return;
+    if (availableSellHoldings.length === 0) return;
+    applyHoldingToDraft(availableSellHoldings[0]);
+  }, [draft.side, matchingHolding, availableSellHoldings]);
+
   async function copyIdentifier(kind: 'trade' | 'order', value: string | null | undefined) {
     if (!value) return;
     try {
@@ -950,7 +972,7 @@ export function SimpleView() {
           <CardHeader>
             <div>
               <CardTitle className="uppercase">{editingSetupId ? 'Edit setup' : 'New setup'}</CardTitle>
-              <CardDescription>Saved trigger workflow, not an immediate broker order</CardDescription>
+              <CardDescription>Build a short-term buy plan or attach a managed profit exit to an existing holding.</CardDescription>
             </div>
             <Button
               type="button"
@@ -974,6 +996,74 @@ export function SimpleView() {
 
           <CardContent>
           <form className="space-y-6" onSubmit={handleSubmit}>
+            <div className="grid gap-3 md:grid-cols-2">
+              <button
+                type="button"
+                onClick={() => {
+                  setError(null);
+                  setMessage(null);
+                  setDraft((prev) => ({ ...prev, side: 'buy' }));
+                }}
+                className={`rounded-[1.25rem] border px-4 py-4 text-left transition ${
+                  draft.side === 'buy'
+                    ? 'border-[var(--primary)] bg-[var(--accent-soft)]'
+                    : 'border-[var(--border)] bg-[var(--card-elevated)]'
+                }`}
+              >
+                <div className="text-[11px] font-black uppercase tracking-[0.24em] text-[var(--muted-foreground)]">Create plan</div>
+                <div className="mt-1 text-sm font-semibold text-[var(--foreground)]">New short-term buy plan</div>
+                <div className="mt-1 text-sm text-[var(--muted-foreground)]">Arm a dip-buy trigger and let the app manage the profit exit after fill.</div>
+              </button>
+              <button
+                type="button"
+                onClick={() => {
+                  setError(null);
+                  setMessage(null);
+                  if (availableSellHoldings.length > 0) {
+                    applyHoldingToDraft(availableSellHoldings[0]);
+                  } else {
+                    setDraft((prev) => ({ ...prev, side: 'sell' }));
+                  }
+                }}
+                className={`rounded-[1.25rem] border px-4 py-4 text-left transition ${
+                  draft.side === 'sell'
+                    ? 'border-[var(--primary)] bg-[var(--accent-soft)]'
+                    : 'border-[var(--border)] bg-[var(--card-elevated)]'
+                }`}
+              >
+                <div className="text-[11px] font-black uppercase tracking-[0.24em] text-[var(--muted-foreground)]">Manage holding</div>
+                <div className="mt-1 text-sm font-semibold text-[var(--foreground)]">Attach an exit plan</div>
+                <div className="mt-1 text-sm text-[var(--muted-foreground)]">Choose an existing holding and place it back under managed profit-taking.</div>
+              </button>
+            </div>
+
+            {draft.side === 'sell' && (
+              <label className="space-y-2">
+                <span className="text-[11px] font-black uppercase tracking-[0.24em] text-zinc-700">Existing holding</span>
+                <Select
+                  value={matchingHolding?.symbol || normalizedSymbol}
+                  onChange={(e) => {
+                    const selected = availableSellHoldings.find((holding) => holding.symbol === e.target.value);
+                    if (selected) applyHoldingToDraft(selected);
+                  }}
+                  disabled={availableSellHoldings.length === 0}
+                >
+                  {availableSellHoldings.length === 0 ? (
+                    <option value="">No eligible holdings available</option>
+                  ) : (
+                    availableSellHoldings.map((holding) => (
+                      <option key={`${holding.symbol}:${holding.tradeId || 'holding'}`} value={holding.symbol}>
+                        {holding.symbol} · {holding.size} @ {holding.entryPrice.toFixed(4)}
+                      </option>
+                    ))
+                  )}
+                </Select>
+                <span className="block text-[11px] text-[var(--muted-foreground)]">
+                  Trade Plans can manage an existing filled holding by attaching a profit exit target to it.
+                </span>
+              </label>
+            )}
+
             <div className="grid gap-4 md:grid-cols-2">
               <label className="space-y-2">
                 <span className="text-[11px] font-black uppercase tracking-[0.24em] text-zinc-700">Symbol</span>
@@ -1037,7 +1127,7 @@ export function SimpleView() {
                   onChange={(e) => updateDraft('side', e.target.value as SimpleSide)}
                 >
                   <option value="buy">Buy the dip + profit exit</option>
-                  <option value="sell">Sell existing Simple holding at profit</option>
+                  <option value="sell">Manage existing holding at profit</option>
                 </Select>
               </label>
             </div>