Editable strike in legs — re-prices from loaded chain

The Strike cell becomes a dropdown of available strikes (for that leg's
symbol+expiry+type) drawn from the cached chain — seeded from chain.html's
last-loaded chain (localStorage) and refreshed by the strategy page's own
per-expiry chain fetch on open / Reload. Picking a new strike updates the
leg's entry price, IV and mark from that contract and clears the lock.

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

frontend/strategy.html

@@ -165,7 +165,12 @@
                       </td>
                       <td style="width:5rem"><input type="number" min="1" step="1" class="form-control form-control-sm" :value="lv.qty" @change="updateLeg(lv.id, { qty: Math.max(1, Math.round(+$event.target.value||1)) })"></td>
                       <td><span class="badge" :class="lv.type==='call' ? 'bg-success-lt text-success' : 'bg-danger-lt text-danger'" x-text="lv.type"></span></td>
-                      <td class="text-end mono" x-text="lv.strike"></td>
+                      <td class="text-end mono" style="width:7rem">
+                        <select x-show="hasStrikeOpts(lv)" class="form-select form-select-sm text-end" :value="lv.strike" @change="changeStrike(lv.id, +$event.target.value)" title="Change strike — entry price, IV & mark update from the loaded chain">
+                          <template x-for="k in strikeOpts(lv)" :key="k"><option :value="k" x-text="k"></option></template>
+                        </select>
+                        <span x-show="!hasStrikeOpts(lv)" x-text="lv.strike"></span>
+                      </td>
                       <td class="mono small" x-text="lv.expiry"></td>
                       <td style="width:8.5rem">
                         <div class="input-group input-group-sm flex-nowrap">
@@ -314,15 +319,59 @@
         refreshing: false, showManual: false, toast: '',
         manual: { side:'long', type:'call', qty:1, strike:null, expiry:'', entryPrice:null, ivPct:null },
         chart: null, _renderTimer: null,
+        _chainCache: {},   // "SYMBOL@EXPIRY" -> { "strike@type": optionRow }
 
         init() {
           this.reload();
-          // pull live spot / marks / IVs on open (does NOT touch entry prices)
+          this._chainCache = this._seedChainCache();
+          // pull live spot / marks / IVs (and per-expiry chains) on open
           if (this.legs.length > 0 && this.symbol) this.reloadMarket(false);
           // re-sync if another tab changed the basket
           window.addEventListener('storage', (e) => { if (e.key === StrategyStore.KEY) this.reload(); });
         },
 
+        // seed the strike picker from whatever chain was last loaded on chain.html
+        _seedChainCache() {
+          try {
+            const vs = (typeof ViewState !== 'undefined') ? ViewState.load('chain') : null;
+            if (!vs || !vs.symbol || !vs.expiry) return {};
+            const map = {};
+            for (const o of (vs.calls || [])) map[Number(o.strike) + '@call'] = o;
+            for (const o of (vs.puts  || [])) map[Number(o.strike) + '@put']  = o;
+            return Object.keys(map).length ? { [vs.symbol + '@' + vs.expiry]: map } : {};
+          } catch { return {}; }
+        },
+
+        _legMap(lv) { return this._chainCache[lv.symbol + '@' + lv.expiry] || null; },
+        hasStrikeOpts(lv) {
+          const m = this._legMap(lv);
+          if (!m) return false;
+          for (const k of Object.keys(m)) if (k.endsWith('@' + lv.type)) return true;
+          return false;
+        },
+        strikeOpts(lv) {
+          const m = this._legMap(lv);
+          const out = [];
+          if (m) for (const k of Object.keys(m)) { if (k.endsWith('@' + lv.type)) out.push(parseFloat(k)); }
+          if (!out.includes(lv.strike)) out.push(lv.strike);
+          return out.sort((a, b) => a - b);
+        },
+        changeStrike(id, newStrike) {
+          const leg = this.legs.find(l => l.id === id);
+          if (!leg || !Number.isFinite(newStrike) || newStrike === leg.strike) return;
+          const m = this._legMap(leg);
+          const o = m && m[Number(newStrike) + '@' + leg.type];
+          const patch = { strike: newStrike };
+          if (o) {
+            const mid = Math.round(((o.midPrice ?? o.mid ?? o.bsPrice ?? leg.entryPrice) || 0) * 100) / 100;
+            patch.entryPrice = mid;
+            patch.currentMark = mid;
+            if (o.iv > 0) patch.iv = o.iv;
+            patch.locked = false;   // it's a different contract now — start fresh
+          }
+          this.updateLeg(id, patch);
+        },
+
         reload() {
           const st = StrategyStore.load();
           this.symbol = st.symbol || '';
@@ -492,6 +541,10 @@
               }
               byExpiry[exp] = map;
             }
+            // make these chains available to the strike picker
+            const cacheAdds = {};
+            for (const exp of Object.keys(byExpiry)) cacheAdds[this.symbol + '@' + exp] = byExpiry[exp];
+            this._chainCache = { ...this._chainCache, ...cacheAdds };
             const st = StrategyStore.load();
             let updated = 0, relinked = 0;
             for (const leg of st.legs) {