fix: guard Corrections against async read from compose

all() returns List.copyOf(entries), which iterates; add()/load()
structurally modify. Once Task 10 wires all() into runTaskAsynchronously
and Task 11 wires add() from the main-thread /ia corrigir command,
the race throws ConcurrentModificationException. Guarded by entries'
own monitor like Conversations: file parse and YAML save stay outside
the lock, only fast in-memory work is under it.

src/main/java/dev/marcospaulo/canalhandia/Corrections.java

@@ -22,6 +22,15 @@ final class Corrections {
     }
 
     private final File file;
+    /**
+     * Read by {@link #all()} from the async answer thread (Ai.compose) and
+     * mutated by {@link #add()}/{@link #load()} from the main thread (/ia
+     * corrigir). Guarded by its own monitor, like {@link Conversations}: only
+     * fast, in-memory work happens under the lock — file parsing and the YAML
+     * save stay outside it — so {@link #all()}'s {@code List.copyOf} never
+     * races a structural change and throws no
+     * {@code ConcurrentModificationException}.
+     */
     private final List<Entry> entries = new ArrayList<>();
 
     Corrections(File file) {
@@ -30,11 +39,12 @@ final class Corrections {
     }
 
     void load() {
+        YamlConfiguration yaml = file.exists() ? YamlConfiguration.loadConfiguration(file) : null;
+        synchronized (entries) {
             entries.clear();
-        if (!file.exists()) {
+            if (yaml == null) {
                 return;
             }
-        YamlConfiguration yaml = YamlConfiguration.loadConfiguration(file);
             for (String key : yaml.getKeys(false)) {
                 String question = yaml.getString(key + ".pergunta");
                 String answer = yaml.getString(key + ".resposta");
@@ -43,14 +53,17 @@ final class Corrections {
                 }
             }
         }
+    }
 
     void add(String question, String answer) {
-        entries.add(new Entry(question, answer));
         YamlConfiguration yaml = new YamlConfiguration();
+        synchronized (entries) {
+            entries.add(new Entry(question, answer));
             for (int i = 0; i < entries.size(); i++) {
                 yaml.set("c" + i + ".pergunta", entries.get(i).question());
                 yaml.set("c" + i + ".resposta", entries.get(i).answer());
             }
+        }
         try {
             yaml.save(file);
         } catch (Exception e) {
@@ -59,8 +72,10 @@ final class Corrections {
     }
 
     List<Entry> all() {
+        synchronized (entries) {
             return List.copyOf(entries);
         }
+    }
 
     /** Corrections sharing at least one significant word with the question. */
     static List<Entry> matching(List<Entry> all, String question) {