IRC: edit server settings as a draft, applied under the service lock

The IRC App edited the live config while the IRC task could be reading
it to connect. The App now edits a copy; applyConfig() validates it and
swaps it in under the lock, and the task connects from a snapshot.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/apps/irc_app.cpp

@@ -98,6 +98,7 @@ bool IrcApp::onChatKey(const KeyEvent& e) {
             input_.setText("");
             scroll_ = 0;
             if (lowered(text) == "/settings") {
+                draft_.reset(new IrcConfig(irc_.draftConfig()));
                 page_ = Page::Settings;
                 fields_.setCount(kFields);
                 break;
@@ -127,7 +128,7 @@ std::string IrcApp::fieldLabel(int f) const {
 }
 
 std::string IrcApp::fieldValue(int f) const {
-    const IrcConfig& c = irc_.config();
+    const IrcConfig& c = *draft_;
     auto secret = [](const std::string& s) { return s.empty() ? std::string("-") : std::string("(set)"); };
     switch (f) {
         case kHost: return c.host;
@@ -144,7 +145,7 @@ std::string IrcApp::fieldValue(int f) const {
 }
 
 void IrcApp::startEditing(int f) {
-    const IrcConfig& c = irc_.config();
+    const IrcConfig& c = *draft_;
     fieldEditor_ = LineEditor(f == kAutojoin ? 200 : 63);
     switch (f) {
         case kHost: fieldEditor_.setText(c.host); break;
@@ -158,7 +159,7 @@ void IrcApp::startEditing(int f) {
 }
 
 void IrcApp::finishEditing() {
-    IrcConfig& c = irc_.config();
+    IrcConfig& c = *draft_;
     const std::string& v = fieldEditor_.text();
     switch (fields_.selected()) {
         case kHost: c.host = v; break;
@@ -185,12 +186,12 @@ bool IrcApp::onSettingsKey(const KeyEvent& e) {
         }
         return true;
     }
-    IrcConfig& c = irc_.config();
+    IrcConfig& c = *draft_;
     switch (e.key) {
         case Key::Up: fields_.up(); break;
         case Key::Down: fields_.down(); break;
         case Key::Back:
-            c.load(c.nick);  // discard unsaved edits
+            draft_.reset();  // discard unsaved edits
             page_ = Page::Chat;
             break;
         case Key::Select:
@@ -201,7 +202,7 @@ bool IrcApp::onSettingsKey(const KeyEvent& e) {
                     c.pinnedSha256.clear();
                     break;
                 case kSave: {
-                    std::string error = irc_.saveConfig();
+                    std::string error = irc_.applyConfig(c);
                     if (!error.empty()) {
                         warn(error);
                         break;