Run cargo fmt on the unit code and drop a quantity box's invalid mark when its line is removed

The new CI runs cargo fmt --check. QuantityInput also reported its validity only when it changed, so removing a line
whose quantity box held bad text left that box counted as invalid and blocked issuing; it now reports valid when it
unmounts, and no longer writes a ref during render.

Claude-Session: https://claude.ai/code/session_01PZypiWDfMkDTeEPeXjRhW5

src-tauri/src/units.rs

@@ -31,7 +31,10 @@ pub fn is_known(unit: &str) -> bool {
 
 /// The ERPNext UOM that suits a built-in unit.
 pub fn default_uom(unit: &str) -> Option<&'static str> {
-    KNOWN.iter().find(|(id, _)| *id == unit).map(|(_, uom)| *uom)
+    KNOWN
+        .iter()
+        .find(|(id, _)| *id == unit)
+        .map(|(_, uom)| *uom)
 }
 
 fn custom_problem(text: &str) -> Option<String> {
@@ -40,11 +43,14 @@ fn custom_problem(text: &str) -> Option<String> {
         return Some("a unit is required".into());
     }
     if t.chars().count() > MAX_CUSTOM_LEN {
-        return Some(format!("a custom unit has at most {MAX_CUSTOM_LEN} characters"));
+        return Some(format!(
+            "a custom unit has at most {MAX_CUSTOM_LEN} characters"
+        ));
     }
     let mut chars = t.chars();
     let first_ok = chars.next().is_some_and(|c| c.is_ascii_alphanumeric());
-    if !first_ok || !chars.all(|c| c.is_ascii_alphanumeric() || matches!(c, ' ' | '.' | '/' | '-')) {
+    if !first_ok || !chars.all(|c| c.is_ascii_alphanumeric() || matches!(c, ' ' | '.' | '/' | '-'))
+    {
         return Some("a unit may use letters, digits, spaces, . / and - only".into());
     }
     None
@@ -113,7 +119,10 @@ mod tests {
 
     #[test]
     fn fractional_units_do_not_map_to_whole_number_uoms() {
-        for id in ["second", "minute", "hour", "day", "week", "month", "km", "m", "sqft", "sqm", "kg", "litre"] {
+        for id in [
+            "second", "minute", "hour", "day", "week", "month", "km", "m", "sqft", "sqm", "kg",
+            "litre",
+        ] {
             assert_ne!(default_uom(id), Some("Nos"), "{id}");
         }
     }