Translate the new Selection labels, and pin what SELECTIONPREVIEW's bits do

The ten strings the Options card gained were English in nineteen of the
twenty-one locales. They are now translated in all of them, using the words
each locale already uses for the surrounding labels — de-DE "Griffe",
fr-FR "Poignées", zh-CN "夹点", zh-TW "掣點" and so on for grips, and the
same for selection, preview and object. System-variable names stay in Latin
uppercase, as they already do in every locale's SETVAR listing.

Composing them from existing keys, the way el-GR composes the neighbouring
labels, only worked for one of the ten: there is no existing key for "limit",
"unlimited", "shift", "rectangle" or "lasso", and "Grips: Objects" as the
label of a numeric limit would read worse than English.

The rollover preview was reported as possibly not working. It works, and now
says so: `the_idle_rollover_follows_bit_one` drives a settled hover over a
line and checks what the scene highlighted, for all four values of the
bitmask. Bit 1 alone highlights, bit 2 alone does not, both do, neither does
not. That is the assertion the inverted config comment would have made
someone doubt — the pick simply needs the cursor still for the 500 ms of
`HOVER_DWELL_MS` before it runs.

Co-Authored-By: Claude Opus 5 <[email protected]>

src/app/update/viewport.rs

@@ -5774,3 +5774,57 @@ properties={:.1}ms picked={}",
         Task::none()
     }
 }
+
+#[cfg(test)]
+mod selection_preview_tests {
+    use super::*;
+    use crate::app::{HoverDwell, OpenCADStudio, HOVER_DWELL_MS};
+
+    /// Drive one settled rollover pick over a line and report what the scene
+    /// ended up highlighting.
+    fn rollover_hits(preview: u8) -> bool {
+        let mut app = OpenCADStudio::new_for_test();
+        app.automation_op(r#"{"op":"new"}"#);
+        let i = app.active_tab;
+        app.model_space.selection_preview = preview;
+        let _ = app.run_command_line("LINE 0,0 10,10");
+        app.tabs[i].scene.selection.borrow_mut().vp_size = (800.0, 600.0);
+        let _ = app.run_command_line("ZOOM EXTENTS");
+
+        // The pick only runs once the cursor has been still for the dwell
+        // window, so the arming timestamp is backdated past it.
+        app.hover_dwell = Some(HoverDwell {
+            last_move_at: Instant::now()
+                - std::time::Duration::from_millis(HOVER_DWELL_MS as u64 * 2),
+            point: iced::Point::new(400.0, 300.0),
+            tile_size: (800.0, 600.0),
+            tab: i,
+        });
+        let _ = app.on_hover_dwell_tick();
+        app.tabs[i].scene.hover_highlight.is_some()
+    }
+
+    /// Bit 1 of `SELECTIONPREVIEW` is the rollover that runs with no command
+    /// active, and the Options card gives it a checkbox. The config comment
+    /// used to describe the bits the wrong way round, so which bit does what
+    /// is worth asserting rather than reading.
+    #[test]
+    fn the_idle_rollover_follows_bit_one() {
+        assert!(
+            rollover_hits(1),
+            "bit 1 set: the line under the cursor must be highlighted",
+        );
+        assert!(
+            rollover_hits(3),
+            "both bits set: still highlighted",
+        );
+        assert!(
+            !rollover_hits(0),
+            "preview off: nothing may be highlighted",
+        );
+        assert!(
+            !rollover_hits(2),
+            "only the in-command bit: the idle rollover stays off",
+        );
+    }
+}