v0.9.7: a turn that cannot hang, a session list that reads nothing twice, and PDFs

- consent: on_permission / on_ask_user wait at most two / five minutes, and in
  the background (a phone off screen, a window that is gone) the answer is
  refused at once with a reason -- a dialog nobody can see blocked the worker
  for good, which is what "the app hangs while the agent works" looked like.
- finishTurn() no longer joins the thread it is called from; the event loop
  reaps the Turn instead.
- AndroidTools: the hop to the GUI thread pings first and gives up after 3 s
  instead of waiting forever on a busy GUI thread.
- the session list stopped reading every transcript: cst_agent_store_info()
  counts newlines in 64 KiB blocks (first_user only within the first 256 KiB),
  and AgentCore::sessions() reuses a row while (mtime, size) is unchanged.
- session_search gets a budget (max_bytes 32 MB, max_seconds 5 s), skips lines
  over 64 KiB, and says when the budget stopped the walk.
- the header shows the phase ("shell: make -j8"), so a long turn no longer
  looks like a stuck one.
- md_to_pdf: the front end's own Qt tool (owner app:qt, every platform):
  markdown or a workspace .md/.html becomes an A4 PDF with 15 mm margins,
  paginated by hand, written into the workspace and delivered as a file card.
  No PrintSupport, so the phone gets it too.
- --uitest runs md_to_pdf through the registry with Chinese text and checks the
  bytes are a PDF; app/CMakeLists.txt no longer drops src/web_md.c from the
  standalone engine build, which the window needs to render markdown.

Version 0.9.7.

app/src/core/AgentCore.h

@@ -9,6 +9,7 @@
 #define CST_APP_AGENTCORE_H
 
 #include <QByteArray>
+#include <QHash>
 #include <QMutex>
 #include <QObject>
 #include <QString>
@@ -204,6 +205,11 @@ class AgentCore : public QObject {
   void permissionRequested(const QString &tool, const QString &detail,
                            const QString &preview);
   void questionAsked(const QString &question, const QString &options);
+  /* The worker asked and nobody answered in time (or the app was in the
+   * background, where the dialog cannot be seen): the turn went on with a
+   * refusal, and the window puts its dialog away again. */
+  void permissionExpired(const QString &tool);
+  void questionExpired();
   void turnFinished(int rc, const QString &err);
   void runningChanged();
   void workspaceChanged();
@@ -218,6 +224,10 @@ class AgentCore : public QObject {
   void syncConfig();
   /* Re-read what a session switch changed (id, todo) and say so. */
   void afterSessionChange();
+  /* True when the app is not on screen: a phone in the background (Qt
+   * suspends it), or a window that is not there at all. A dialog opened now
+   * would be invisible, so consent is refused instead of waited for. */
+  bool backgrounded() const;
 
   /* Hook trampolines (C, run on the worker thread). */
   static void hookStatus(const char *msg, void *ud);
@@ -255,6 +265,15 @@ class AgentCore : public QObject {
   bool m_permPending = false;
   QString m_question;
   QString m_todo;
+  /* The session list rebuilt only when a transcript moved: filling one row
+   * walks the whole file, and the sidebar asks for the list on every store
+   * change. Keyed by id, dropped when the id is gone. */
+  struct SessionCache {
+    qint64 mtime = 0;
+    qint64 size = 0;
+    QVariantMap row;
+  };
+  mutable QHash<QString, SessionCache> m_sessionCache;
   /* Names of the files this window attached, in the engine's pending order:
    * the engine's own description says what it is, not where it came from. */
   QStringList m_attachNames;