Make bare /quit disconnect only that server, keep windows open, bump to 0.1.9

/quit now disconnects the window's server without closing anything: every
buffer of that server and wIRC main get a "Disconnected" line, the server card
shows Disconnected with its Connect button, history is flushed to disk, and
there's no auto-reconnect. Connect rejoins the channels we were in (including
ones joined with /join, now tracked) into the still-open windows. Sending while
disconnected shows a "Not connected" line in that window. Exit wIRC still
disconnects everything and closes the app.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

build.gradle.kts

@@ -6,7 +6,7 @@ plugins {
 }
 
 group = "com.tpuahsiew.wirc"
-version = "0.1.8"
+version = "0.1.9"
 
 // No project-level repositories{} block here: settings.gradle.kts sets
 // dependencyResolutionManagement.repositoriesMode = FAIL_ON_PROJECT_REPOS and already
@@ -38,7 +38,7 @@ compose.desktop {
             appResourcesRootDir.set(project.file("installerResources"))
             targetFormats(TargetFormat.Msi, TargetFormat.Exe)
             packageName = "wIRC"
-            packageVersion = "0.1.8"
+            packageVersion = "0.1.9"
             windows {
                 menuGroup = "wIRC"
                 upgradeUuid = "8f14e45f-ceea-4a5e-9c3b-5b1f0e8c2b7a"