Give the memory back when a local model has been sitting unused

A whisper.cpp or llama.cpp server started for one dictation stayed loaded
until Dikte quit. On this machine that is 1.3 GB of VRAM for large-v3 plus
whatever the cleanup LLM takes, held all day between dictations that last
seconds.

Each Server now carries an idle window. A watcher thread per launch stops the
server once nothing has asked it anything for that long, and the next request
loads it again through serve(), which already starts what is not running.
Settings has one checkbox and one number for both servers, on by default at ten
minutes, and it only appears for a machine that runs a model here. The tray menu
says which models are loaded and offers to unload them now.

Two things the clock alone gets wrong, both held off by a count of requests in
flight:

  * A file or a meeting is one address lookup and then minutes of work, which
    to a clock started at the lookup looks exactly like a model nobody wants.
    api.py and cleanup.py hold the count for the length of the request.

  * The count must survive the start it triggered. cleanup._local takes the
    hold and only then asks for the address, so a cold start happens inside it;
    neither serve() nor _stop_now() resets the count any more.

Unloading by hand runs on the interface's thread, so it asks for the start lock
rather than waiting on it: a model still being read in is refused, the way one
in the middle of a request is, instead of freezing the window for as long as
the load takes.

dikte/settings_ui.py

@@ -1309,9 +1309,47 @@ class SettingsWindow(QDialog):
         orr_form.addRow(self.local_llm_options)
 
         outer.addWidget(orr)
+
+        # One box for both servers rather than a row inside each: what is being
+        # decided is whether this machine keeps gigabytes tied up between
+        # dictations, and that is not a question anybody wants to answer once
+        # per model.
+        self.local_box = QGroupBox(t("Models on this machine"))
+        local_form = QFormLayout(self.local_box)
+        self.local_idle_unload = QCheckBox(t("Unload a model that is sitting unused"))
+        self.local_idle_unload.setToolTip(
+            t("A loaded model holds its memory whether anything is using it or "
+              "not: over a gigabyte for whisper, several for an LLM. Unloading "
+              "gives that back to the rest of the desktop, and the next "
+              "dictation loads it again at the cost of the seconds that takes."))
+        self.local_idle_minutes = QSpinBox()
+        self.local_idle_minutes.setRange(1, 720)
+        self.local_idle_minutes.valueChanged.connect(self._idle_suffix)
+        self._idle_suffix(self.local_idle_minutes.value())
+        self.local_idle_unload.toggled.connect(self.local_idle_minutes.setEnabled)
+        local_form.addRow("", self.local_idle_unload)
+        local_form.addRow(t("After"), self.local_idle_minutes)
+        outer.addWidget(self.local_box)
+
         outer.addStretch(1)
         return page
 
+    def _idle_suffix(self, minutes):
+        """The spin box's own noun, since its lowest value is one of them.
+
+        Turkish is handed both and translates them the same: a number there is
+        followed by the singular however many it counts.
+        """
+        self.local_idle_minutes.setSuffix(
+            t(" minute") if minutes == 1 else t(" minutes"))
+
+    def _refresh_local_box(self):
+        """The idle unload is only on screen when something here runs locally."""
+        self.local_box.setVisible(
+            (self.transcribe_provider.currentData() or "local") == "local"
+            or (self.cleanup_provider.currentData() or "openrouter") == "local"
+        )
+
     def _prompt_tab(self):
         page = QWidget()
         layout = QVBoxLayout(page)
@@ -2078,6 +2116,9 @@ class SettingsWindow(QDialog):
         self.local_llm_preload.setChecked(conf["local_llm_preload"])
         self._select_data(self.local_llm_reasoning, conf["local_llm_reasoning"])
         self.local_llm.load(conf["local_llm_model"], conf["local_llm_repo"])
+        self.local_idle_unload.setChecked(conf["local_idle_unload"])
+        self.local_idle_minutes.setValue(int(conf["local_idle_minutes"]))
+        self.local_idle_minutes.setEnabled(conf["local_idle_unload"])
         # The defaults as they read NOW, kept for the save comparison: after a
         # language switch the boxes still hold the old language's default, and
         # comparing against the new one would store that text as a custom
@@ -2209,6 +2250,8 @@ class SettingsWindow(QDialog):
         conf["local_llm_gpu"] = self.local_llm_gpu.isChecked()
         conf["local_llm_preload"] = self.local_llm_preload.isChecked()
         conf["local_llm_reasoning"] = self.local_llm_reasoning.currentData() or ""
+        conf["local_idle_unload"] = self.local_idle_unload.isChecked()
+        conf["local_idle_minutes"] = self.local_idle_minutes.value()
 
         # Store an empty prompt when it matches a default: the one it was
         # loaded with, or today's (a Reset click in a session that switched
@@ -2351,6 +2394,7 @@ class SettingsWindow(QDialog):
         self.stt_form.setRowVisible(self.transcribe_status, not local)
         self.stt_form.setRowVisible(self.local_whisper, local)
         self.stt_form.setRowVisible(self.local_options, local)
+        self._refresh_local_box()
         if local:
             return
         self.transcribe_model.clear()
@@ -2859,6 +2903,7 @@ class SettingsWindow(QDialog):
                                         provider != "local")
         self.cleanup_form.setRowVisible(self.local_llm, provider == "local")
         self.cleanup_form.setRowVisible(self.local_llm_options, provider == "local")
+        self._refresh_local_box()
         binary = cleanup.executable(provider)
         found = shutil.which(binary) if binary else ""
         if provider == "local":