CardDb: make loadCard idempotent (fix latent duplicate-PaperCard bug)

loadCard is not idempotent: addSetCard unconditionally increments the art index
and appends a fresh PaperCard, so a redundant call for a (name, set) printing
already loaded duplicates it in allCardsByName. Skip when that exact (name, set)
printing already exists. Guarding on card-name presence alone would break the
"add a printing from a not-yet-loaded set" path (StaticData.getOrLoadCommonCard),
where the card can exist under other sets while the requested set's printing is
still missing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TGBC7aB5gagjvXk9qCgC2d

Author: shoeless

forge-core/src/main/java/forge/card/CardDb.java

@@ -445,6 +445,12 @@ public void loadCard(String cardName, String setCode, CardRules cr) {
                 return;
             }
         }
+        // idempotency: addSetCard appends unconditionally, so skip if this exact (name,set)
+        // printing is already loaded (guarding on name alone would break the load-new-set path)
+        CardEdition guardEd = editions.get(setCode);
+        if (guardEd != null && !guardEd.equals(CardEdition.UNKNOWN) && hasPrintingInSet(cardName, guardEd)) {
+            return;
+        }
         boolean reIndexNecessary = false;
         CardEdition ed = editions.get(setCode);
         if (ed == null || ed.equals(CardEdition.UNKNOWN)) {
@@ -462,6 +468,18 @@ public void loadCard(String cardName, String setCode, CardRules cr) {
         }
     }
 
+    /** True if a printing of cardName from edition is already loaded (no side effects, unlike getCardFromSet). */
+    private boolean hasPrintingInSet(String cardName, CardEdition edition) {
+        String code1 = edition.getCode(), code2 = edition.getCode2();
+        for (PaperCard pc : getAllCards(cardName)) {
+            String ed = pc.getEdition();
+            if (ed.equalsIgnoreCase(code1) || ed.equalsIgnoreCase(code2)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     public void initialize(boolean logMissingPerEdition, boolean logMissingSummary, boolean enableUnknownCards) {
         Set<String> allMissingCards = new LinkedHashSet<>();
         List<String> missingCards = new ArrayList<>();