Restored the short form of large token numbers

app/MindWork AI Studio/Chat/TokenAmount.cs

@@ -6,11 +6,10 @@ namespace AIStudio.Chat;
 /// Writes a number of tokens the way a person reads it next to their input field.
 /// </summary>
 /// <remarks>
-/// Written out in full up to a million, because below that the short form saves nothing: "11.86k"
-/// and "11,860" are both six characters, and "999.99k" and "999,990" are both seven. All the
-/// prefix does in that range is ask the reader to know what it stands for, and not every reader
-/// does. From a million on it earns its place -- nine characters of digits become five -- and two
-/// decimals there keep the resolution a person acts on.
+/// A context window of a million tokens written out in full is eight characters of noise under a
+/// text field, and nobody reads the last five of them. So everything from a thousand on is
+/// shortened, and two decimals keep the resolution a person acts on: the difference between 1.20k
+/// and 1.80k is one they can see, while the last three digits of 1,234 are not.
 ///
 /// The culture is passed in rather than taken from the thread. AI Studio's language is chosen in
 /// its settings and does not move the thread's culture along with it, so a German who picked German
@@ -21,7 +20,7 @@ public static class TokenAmount
     /// <summary>
     /// Below this, the exact number is shown.
     /// </summary>
-    private const int EXACT_BELOW = 1_000_000;
+    private const int EXACT_BELOW = 1_000;
 
     /// <summary>
     /// Writes a number of tokens.
@@ -34,6 +33,15 @@ public static class TokenAmount
         if (tokens < EXACT_BELOW)
             return tokens.ToString("N0", culture);
 
+        //
+        // Rounded before the unit is chosen, not after. Otherwise the few hundred tokens just below
+        // a million round up inside their own unit and read as "1,000.00k", which is a number
+        // nobody writes.
+        //
+        var thousands = tokens / 1_000d;
+        if (Math.Round(thousands, 2) < 1_000d)
+            return $"{thousands.ToString("N2", culture)}k";
+
         return $"{(tokens / 1_000_000d).ToString("N2", culture)}M";
     }
 }