fix: YAML frontmatter 解析 + call_capability iPet 兼容桥接

- SKILL.md 解析器支持跳过 YAML frontmatter (---...---)
  修复导入的 Claude Code / Agent Skills 的元数据头导致
  description 混入元数据的问题
- call_capability 桥接工具：兼容 iPet 遗留的
  {name, prompt} 调用格式
  按 name 查找 SkillRegistry，委托执行
- 清理 parser 中未使用的 in_desc 变量

src/tools/parser.rs

@@ -38,11 +38,20 @@ pub fn parse_skill(skill_dir: &Path) -> Result<Skill, String> {
     let mut params_fence = 0;
     let mut execute_fence = 0;
     let mut desc_lines: Vec<&str> = Vec::new();
-    let mut in_desc = false;
+    let mut frontmatter_fences = 0;
 
-    for (i, line) in lines.iter().enumerate() {
+    for (_i, line) in lines.iter().enumerate() {
         let trimmed = line.trim();
 
+        // 跳过 YAML frontmatter (---...---)
+        if trimmed == "---" && frontmatter_fences < 2 {
+            frontmatter_fences += 1;
+            continue;
+        }
+        if frontmatter_fences == 1 {
+            continue;
+        }
+
         // 标题行 → 技能名
         if trimmed.starts_with("# ") && !trimmed.starts_with("## ") && name.is_empty() {
             name = trimmed.trim_start_matches("# ").trim().to_string();
@@ -54,24 +63,20 @@ pub fn parse_skill(skill_dir: &Path) -> Result<Skill, String> {
             let section = trimmed.trim_start_matches("## ").trim().to_lowercase();
             match section.as_str() {
                 "risk level" | "risk_level" | "risk" => {
-                    in_desc = false;
                     in_params = false;
                     in_execute = false;
                 }
                 "parameters" | "param" => {
-                    in_desc = false;
                     in_params = true;
                     in_execute = false;
                 }
                 "execute" | "execution" | "command" | "run" => {
-                    in_desc = false;
                     in_params = false;
                     in_execute = true;
                     params_fence = 0;
                     execute_fence = 0;
                 }
                 _ => {
-                    in_desc = false;
                     in_params = false;
                     in_execute = false;
                 }