Fix YahooFinanceClient Swift 6 actor isolation and type-path errors

Two bugs:

1. Swift 6 strict concurrency: JSONDecoder().decode() inside actor-isolated
   methods triggers "Main actor-isolated conformance cannot be used in
   actor-isolated context". Fix: move all Decodable usage into nonisolated
   helper methods (parseChart, parseOptions, makeContract) so the conformance
   is invoked outside the actor's isolation boundary.

2. Wrong nested type path: OptionsResponse.OptionData.YFOption does not exist;
   YFOption is nested directly under OptionsResponse. Fix: reference
   OptionsResponse.YFOption everywhere and remove the old private extension
   in favour of the nonisolated makeContract(from:) factory method.

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

ios/OptionsSidekick/OptionsSidekick/OptionsSidekick/OptionsSidekick/Services/YahooFinanceClient.swift

@@ -72,12 +72,22 @@ actor YahooFinanceClient {
               let typed = entry.value as? T else { return nil }
         return typed
     }
-    private func set(_ value: Any, key: String) {
+    private func set(_ value: Any, key: String) { cache[key] = (value, Date()) }
-        cache[key] = (value, Date())
-    }
     func clearCache() { cache.removeAll() }
 
-    // MARK: Price history
+    // MARK: - nonisolated decode helpers
+    // Placed outside actor isolation so Swift 6 doesn't flag the Decodable
+    // conformance as being used in an actor-isolated context.
+
+    nonisolated private func parseChart(_ data: Data) throws -> ChartResponse {
+        try JSONDecoder().decode(ChartResponse.self, from: data)
+    }
+
+    nonisolated private func parseOptions(_ data: Data) throws -> OptionsResponse {
+        try JSONDecoder().decode(OptionsResponse.self, from: data)
+    }
+
+    // MARK: - Price history
 
     func priceHistory(ticker: String) async throws -> PriceHistory {
         let key = "hist_\(ticker)"
@@ -88,7 +98,7 @@ actor YahooFinanceClient {
         else { throw YFError.badURL }
 
         let (data, _) = try await session.data(from: url)
-        let resp = try JSONDecoder().decode(ChartResponse.self, from: data)
+        let resp = try parseChart(data)
 
         guard let r = resp.chart.result?.first,
               let q = r.indicators.quote.first else { throw YFError.noData }
@@ -116,7 +126,7 @@ actor YahooFinanceClient {
         return result
     }
 
-    // MARK: Option expirations
+    // MARK: - Option expirations
 
     func expirations(ticker: String) async throws -> [Date] {
         let key = "exp_\(ticker)"
@@ -127,7 +137,7 @@ actor YahooFinanceClient {
         else { throw YFError.badURL }
 
         let (data, _) = try await session.data(from: url)
-        let resp = try JSONDecoder().decode(OptionsResponse.self, from: data)
+        let resp = try parseOptions(data)
 
         guard let r = resp.optionChain.result?.first else { throw YFError.noData }
         let dates = r.expirationDates.map { Date(timeIntervalSince1970: Double($0)) }
@@ -148,7 +158,7 @@ actor YahooFinanceClient {
         return exps.first { Calendar.current.isDate($0, inSameDayAs: today) }
     }
 
-    // MARK: Option chain
+    // MARK: - Option chain
 
     func optionChain(ticker: String, expiration: Date) async throws -> OptionChain {
         let epoch = Int(expiration.timeIntervalSince1970)
@@ -160,20 +170,34 @@ actor YahooFinanceClient {
         else { throw YFError.badURL }
 
         let (data, _) = try await session.data(from: url)
-        let resp = try JSONDecoder().decode(OptionsResponse.self, from: data)
+        let resp = try parseOptions(data)
 
         guard let r    = resp.optionChain.result?.first,
               let opts = r.options.first else { throw YFError.noData }
 
-        let calls = opts.calls.compactMap { OptionContract(from: $0) }
+        let calls = opts.calls.compactMap { makeContract(from: $0) }
-        let puts  = opts.puts .compactMap { OptionContract(from: $0) }
+        let puts  = opts.puts .compactMap { makeContract(from: $0) }
 
         let chain = OptionChain(expiration: expiration, calls: calls, puts: puts)
         set(chain, key: key)
         return chain
     }
 
-    // MARK: Earnings date
+    /// nonisolated factory so the OptionsResponse.YFOption type is not
+    /// referenced inside actor-isolated code (avoids Swift 6 conformance error).
+    nonisolated private func makeContract(from yf: OptionsResponse.YFOption) -> OptionContract? {
+        guard let bid = yf.bid, let ask = yf.ask, bid >= 0, ask >= 0 else { return nil }
+        return OptionContract(
+            strike:            yf.strike,
+            bid:               bid,
+            ask:               ask,
+            impliedVolatility: yf.impliedVolatility ?? 0.3,
+            volume:            yf.volume            ?? 0,
+            openInterest:      yf.openInterest      ?? 0
+        )
+    }
+
+    // MARK: - Earnings date
 
     func nextEarningsDate(ticker: String) async throws -> Date? {
         let key = "earn_\(ticker)"
@@ -198,14 +222,14 @@ actor YahooFinanceClient {
         }
 
         let date: Date? = Date(timeIntervalSince1970: rawDate) > Date()
-            ? Date(timeIntervalSince1970: rawDate)
+            ? Date(timeIntervalSince1970: rawDate) : nil
-            : nil
         set(date as Any, key: key)
         return date
     }
 }
 
 // MARK: - Private JSON models
+// Defined at file scope (outside the actor) as plain Decodable value types.
 
 private struct ChartResponse: Decodable {
     let chart: Wrapper
@@ -234,6 +258,7 @@ private struct OptionsResponse: Decodable {
         let calls: [YFOption]
         let puts:  [YFOption]
     }
+    // YFOption is a direct nested type of OptionsResponse, NOT of OptionData.
     struct YFOption: Decodable {
         let strike:            Double
         let bid:               Double?
@@ -243,15 +268,3 @@ private struct OptionsResponse: Decodable {
         let openInterest:      Int?
     }
 }
-
-private extension OptionContract {
-    init?(from yf: OptionsResponse.OptionData.YFOption) {
-        guard let bid = yf.bid, let ask = yf.ask, bid >= 0, ask >= 0 else { return nil }
-        self.strike            = yf.strike
-        self.bid               = bid
-        self.ask               = ask
-        self.impliedVolatility = yf.impliedVolatility ?? 0.3
-        self.volume            = yf.volume            ?? 0
-        self.openInterest      = yf.openInterest      ?? 0
-    }
-}