v0.9.1: the window opens on the session the engine already has open

A workspace is never empty on the second run: cst_agent_open() resumes the
last session of the store, so the engine holds a transcript before the window
exists. The window only filled its view on a session *switch*, and a start is
not a switch -- the pane came up empty next to a sidebar pointing at the very
session it belonged to (on the phone: "hello, 6 messages" highlighted, no
transcript under it).

- Main.qml: Component.onCompleted reloads the session list and replays the
  open session, the same call the sessionChanged handler makes.
- AgentCore::switchSession(): a click on the row of the session that is
  already open emits sessionChanged instead of returning quietly, so the row
  redraws its transcript rather than being a dead spot.
- --uitest: the window is now created over a seeded session (a fixture is
  written and switched to before the QML loads, which is what a restart looks
  like) and the check "the open session is on screen at startup" pins it --
  it failed with 0 rows before the fix. Two qWaits in the settings-dialog
  section, whose clicks were racing the dialog's layout: the extra startup
  work made that visible (5 failures that had nothing to do with sessions).

Verified: --uitest 79/79 (the new check among them), cst-app-selftest OK, and
on the phone -- the APK rebuilt and installed, a restart of the app draws the
whole stored session (messages, tool cards, thinking blocks, copy icons).

Version 0.9.1.

mode = coding

app/src/core/AgentCore.cpp

@@ -551,8 +551,13 @@ bool AgentCore::newSession() {
 bool AgentCore::switchSession(const QString &id) {
   if (!m_agent || m_running || id.isEmpty())
     return false;
-  if (id == sessionId())
+  if (id == sessionId()) {
+    /* A click on the row of the session that is already open: nothing to
+     * switch, but the window still wants the transcript (the row is not a
+     * dead spot), and sessionChanged is what draws it. */
+    emit sessionChanged();
     return true;
+  }
   if (cst_agent_switch_session(m_agent, id.toUtf8().constData()) != 0)
     return false;
   afterSessionChange();

app/src/ui/UiTest.cpp

@@ -196,6 +196,15 @@ int runUiTest(AgentCore &core, const QString &size) {
     }
   }
 
+  /* A workspace is never empty on a second run: the engine opens the last
+   * session of the store (cst_agent_open()), so the window is created with a
+   * transcript already in the engine. Put one there before the QML loads,
+   * which is exactly what a restart looks like. */
+  const QString resumed =
+      writeFixtureSession(core.workspace(), QStringLiteral("20260101-115959-on"));
+  check(!resumed.isEmpty() && core.switchSession(resumed),
+        QStringLiteral("the engine has a session open before the window exists"));
+
   QQmlApplicationEngine engine;
   installThemeIcons(&engine); /* the window's icons, same as main() */
   /* image://cstattach/: the session's stored images, pointed at the session
@@ -219,6 +228,15 @@ int runUiTest(AgentCore &core, const QString &size) {
   }
   QTest::qWait(250);
 
+  /* --- the window opens on the session the engine already had ----------- */
+  {
+    QQuickItem *tr = item(win, QStringLiteral("transcript"));
+    const int rows = tr ? tr->property("count").toInt() : -1;
+    check(rows == 5,
+          QStringLiteral("the open session is on screen at startup (%1 rows)")
+              .arg(rows));
+  }
+
   QQuickItem *docked = item(win, QStringLiteral("dockedSidebar"));
   QQuickItem *navButton = item(win, QStringLiteral("navButton"));
   QQuickItem *navPanel = item(win, QStringLiteral("navPanel"));
@@ -464,8 +482,10 @@ int runUiTest(AgentCore &core, const QString &size) {
   /* The dialog drives the same two engine calls: open it, fold the advanced
    * section out and put a provider in through the form. */
   clickMouse(win, QStringLiteral("settingsButton"));
+  QTest::qWait(150); /* the dialog's layout settles before it is clicked into */
   if (panel && mfield) {
     clickMouse(win, QStringLiteral("settingsAdvanced"));
+    QTest::qWait(150); /* the fold-out re-lays the body out */
     QQuickItem *nfield = item(win, QStringLiteral("advName"));
     QQuickItem *bfield = item(win, QStringLiteral("advBase"));
     check(nfield && nfield->isVisible(), QStringLiteral("Advanced options opens in the dialog"));