Add clear-board button and clipboard auto-watch toggle

Board.clear() drops the Nest position, spotters, reference points, and
targets; wired to a header button behind a confirm dialog since it's
not reversible.

The clipboard-watch toggle connects to Gdk.Clipboard's 'changed'
signal and re-runs the merge-all OCR flow automatically whenever the
clipboard gains new image content, skipping non-image changes (e.g.
text copied elsewhere) so it doesn't spam toasts. Off by default.
Disconnected on window destroy.

src/fenigma/app.py

@@ -152,6 +152,7 @@ class MainWindow(Adw.ApplicationWindow):
         _install_css()
 
         self.board = Board()
+        self._clipboard_watch_handler = None
 
         self.toast_overlay = Adw.ToastOverlay()
         self.set_content(self.toast_overlay)
@@ -178,6 +179,13 @@ class MainWindow(Adw.ApplicationWindow):
         clip_btn.connect("clicked", lambda _b: self._fetch_clipboard())
         header.pack_start(clip_btn)
 
+        self._watch_btn = Gtk.ToggleButton(icon_name="media-playback-start-symbolic")
+        self._watch_btn.set_tooltip_text(
+            "Auto-watch clipboard: apply new screenshots as soon as they're copied"
+        )
+        self._watch_btn.connect("toggled", self._on_toggle_clipboard_watch)
+        header.pack_start(self._watch_btn)
+
         header.pack_start(Gtk.Separator(orientation=Gtk.Orientation.VERTICAL))
 
         for label, popover_builder in (
@@ -193,6 +201,11 @@ class MainWindow(Adw.ApplicationWindow):
         strike_btn.connect("clicked", lambda _b: self._add_strike())
         header.pack_start(strike_btn)
 
+        clear_btn = Gtk.Button(icon_name="edit-clear-all-symbolic")
+        clear_btn.set_tooltip_text("Clear board (drop everything)")
+        clear_btn.connect("clicked", lambda _b: self._clear_board())
+        header.pack_start(clear_btn)
+
         firing_btn = Gtk.Button(icon_name="sidebar-show-right-symbolic")
         firing_btn.set_tooltip_text("Firing commands")
         firing_btn.connect("clicked", lambda _b: self._toggle_firing_panel())
@@ -235,6 +248,7 @@ class MainWindow(Adw.ApplicationWindow):
             )
         )
         self.add_controller(controller)
+        self.connect("destroy", self._on_window_destroy)
 
     # -- generic helpers -----------------------------------------------------
     def _make_menu_button(self, label: str, build_popover) -> Gtk.MenuButton:
@@ -334,6 +348,58 @@ class MainWindow(Adw.ApplicationWindow):
 
         on_parsed(info)
 
+    def _on_toggle_clipboard_watch(self, btn: Gtk.ToggleButton) -> None:
+        """Auto-watch toggle: while on, every clipboard change that looks
+        like an image (not e.g. text copied elsewhere) is OCR'd and merged
+        automatically, no manual fetch needed between screenshots."""
+        clipboard = Gdk.Display.get_default().get_clipboard()
+        if btn.get_active():
+            self._clipboard_watch_handler = clipboard.connect("changed", self._on_clipboard_changed)
+            btn.set_icon_name("media-playback-stop-symbolic")
+            btn.set_tooltip_text("Auto-watch clipboard: on, click to stop")
+            self.toast("Watching clipboard, new screenshots apply automatically.")
+        else:
+            if self._clipboard_watch_handler is not None:
+                clipboard.disconnect(self._clipboard_watch_handler)
+                self._clipboard_watch_handler = None
+            btn.set_icon_name("media-playback-start-symbolic")
+            btn.set_tooltip_text("Auto-watch clipboard: apply new screenshots as soon as they're copied")
+
+    def _on_clipboard_changed(self, clipboard: Gdk.Clipboard) -> None:
+        formats = clipboard.get_formats()
+        if formats is None or not formats.contain_gtype(Gdk.Texture):
+            return  # not an image (e.g. text copied elsewhere), ignore quietly
+        self._run_ocr_from_clipboard(self._merge_all)
+
+    def _on_window_destroy(self, *_a) -> None:
+        if self._clipboard_watch_handler is not None:
+            Gdk.Display.get_default().get_clipboard().disconnect(self._clipboard_watch_handler)
+            self._clipboard_watch_handler = None
+
+    def _clear_board(self) -> None:
+        board = self.board
+        if board.nest.coord is None and not board.spotters and not board.reference_points and not board.targets:
+            return  # nothing to clear
+        dialog = Adw.AlertDialog(
+            heading="Clear board?",
+            body="Drops the Nest position and every spotter, reference point, and target. This can't be undone.",
+        )
+        dialog.add_response("cancel", "Cancel")
+        dialog.add_response("clear", "Clear")
+        dialog.set_response_appearance("clear", Adw.ResponseAppearance.DESTRUCTIVE)
+        dialog.set_default_response("cancel")
+        dialog.set_close_response("cancel")
+        dialog.connect("response", self._on_clear_board_response)
+        dialog.present(self)
+
+    def _on_clear_board_response(self, _dialog, response: str) -> None:
+        if response != "clear":
+            return
+        self.board.clear()
+        self._set_selection(None)
+        self._refresh()
+        self.toast("Board cleared.")
+
     def _merge_all(self, info: "ocr.ParsedInfo") -> None:
         changed = []
         if info.nest_coord is not None:

src/fenigma/models.py

@@ -384,6 +384,17 @@ class Board:
     def remove_target(self, target: Target) -> None:
         self.targets.remove(target)
 
+    # -- reset ----------------------------------------------------------
+    def clear(self) -> None:
+        """Drop everything: Nest position, spotters, reference points,
+        targets. Used by the "clear board" action for a fresh start
+        without restarting the app."""
+        self.nest = Nest()
+        self.spotters.clear()
+        self.reference_points.clear()
+        self.targets.clear()
+        self._spotter_seq = 0
+
     def reorder_target(self, target: Target, new_index: int) -> None:
         """Manual drag-order: `self.targets`' list order is itself the
         persisted order (saved/loaded as a plain JSON array), and is what