fix(SkillFileSystemHelper): Fixed an issue where an existing skill prevented other skills from being saved. (agentscope-ai#1049)

## AgentScope-Java Version
1.0.10
[The version of AgentScope-Java you are working on, e.g. 1.0.9, check
your pom.xml dependency version or run `mvn dependency:tree | grep
agentscope-parent:pom`(only mac/linux)]

## Description

[Please describe the background, purpose, changes made, and how to test
this PR]

当技能目录已存在且强制覆盖标志为false时，现在将跳过该技能而不是返回失败状态。这样可以保存后续技能而不会因为单个技能的存在而导致其他技能无法保存。
## Checklist

Please check the following items before code is ready to be reviewed.

- [x]  Code has been formatted with `mvn spotless:apply`
- [x]  All tests are passing (`mvn test`)
- [ ]  Javadoc comments are complete and follow project conventions
- [ ] Related documentation has been updated (e.g. links, examples,
etc.)
- [x]  Code is ready for review

Author: superjvjkdf

agentscope-core/src/main/java/io/agentscope/core/skill/util/SkillFileSystemHelper.java

@@ -173,6 +173,8 @@ public static boolean saveSkills(Path baseDir, List<AgentSkill> skills, boolean
             return false;
         }
 
+        int size = skills.size();
+        int saveCount = 0;
         try {
             for (AgentSkill skill : skills) {
                 String skillName = skill.getName();
@@ -182,7 +184,7 @@ public static boolean saveSkills(Path baseDir, List<AgentSkill> skills, boolean
                     if (!force) {
                         logger.info(
                                 "Skill directory already exists and force=false: {}", skillName);
-                        return false;
+                        continue; // Skip to the next skill if force=false
                     } else {
                         logger.info("Overwriting existing skill directory: {}", skillName);
                         deleteDirectory(skillDir);
@@ -215,10 +217,15 @@ public static boolean saveSkills(Path baseDir, List<AgentSkill> skills, boolean
                     }
                 }
 
+                saveCount++;
                 logger.info("Successfully saved skill: {}", skillName);
             }
+            boolean allSaved = (size == saveCount);
+            if (!allSaved) {
+                logger.warn("Not all skills were saved. Saved {} of {}", saveCount, size);
+            }
 
-            return true;
+            return allSaved;
         } catch (IOException e) {
             logger.error("Failed to save skills", e);
             throw new RuntimeException("Failed to save skills", e);

agentscope-core/src/test/java/io/agentscope/core/skill/util/SkillFileSystemHelperTest.java

@@ -152,6 +152,72 @@ void testSaveSkills_ExistingSkill_ForceDisabled() {
         assertEquals("Test Skill", loaded.getDescription());
     }
 
+    @Test
+    @DisplayName(
+            "Should save zero skills and leave file contents unchanged when all exist and force is"
+                    + " false")
+    void testSaveSkills_AllExistingSkills_ForceDisabled_NoSkillsSaved() throws IOException {
+        String originalTestSkill =
+                Files.readString(
+                        skillsBaseDir.resolve("test-skill/SKILL.md"), StandardCharsets.UTF_8);
+        String originalAnotherSkill =
+                Files.readString(
+                        skillsBaseDir.resolve("another-skill/SKILL.md"), StandardCharsets.UTF_8);
+
+        AgentSkill skill1 = new AgentSkill("test-skill", "Updated Test", "Updated content 1", null);
+        AgentSkill skill2 =
+                new AgentSkill("another-skill", "Updated Another", "Updated content 2", null);
+
+        boolean result =
+                SkillFileSystemHelper.saveSkills(skillsBaseDir, List.of(skill1, skill2), false);
+
+        // 0 out of 2 saved — no coverage at all
+        assertFalse(result);
+        assertEquals(
+                originalTestSkill,
+                Files.readString(
+                        skillsBaseDir.resolve("test-skill/SKILL.md"), StandardCharsets.UTF_8),
+                "test-skill SKILL.md must not be modified");
+        assertEquals(
+                originalAnotherSkill,
+                Files.readString(
+                        skillsBaseDir.resolve("another-skill/SKILL.md"), StandardCharsets.UTF_8),
+                "another-skill SKILL.md must not be modified");
+    }
+
+    @Test
+    @DisplayName("Should save new skills while leaving existing ones unchanged when force is false")
+    void testSaveSkills_MixedSkills_ForceDisabled_NewSavedExistingUnchanged() throws IOException {
+        String originalContent =
+                Files.readString(
+                        skillsBaseDir.resolve("test-skill/SKILL.md"), StandardCharsets.UTF_8);
+
+        AgentSkill existingSkill =
+                new AgentSkill("test-skill", "Updated Description", "Updated content", null);
+        AgentSkill newSkill = new AgentSkill("brand-new-skill", "Brand New", "New content", null);
+
+        boolean result =
+                SkillFileSystemHelper.saveSkills(
+                        skillsBaseDir, List.of(existingSkill, newSkill), false);
+
+        // 1 out of 2 saved — not all saved
+        assertFalse(result);
+
+        // existing skill must not be modified
+        assertEquals(
+                originalContent,
+                Files.readString(
+                        skillsBaseDir.resolve("test-skill/SKILL.md"), StandardCharsets.UTF_8),
+                "test-skill SKILL.md must not be modified");
+
+        // new skill must be saved correctly
+        AgentSkill loaded =
+                SkillFileSystemHelper.loadSkill(skillsBaseDir, "brand-new-skill", "source");
+        assertEquals("brand-new-skill", loaded.getName());
+        assertEquals("Brand New", loaded.getDescription());
+        assertEquals("New content", loaded.getSkillContent());
+    }
+
     @Test
     @DisplayName("Should overwrite when skill exists and force is true")
     void testSaveSkills_ExistingSkill_ForceEnabled() {