feat: P0 KernelClient功能修复 + P1/P2/P3质量改进

P0 KernelClient 功能断裂修复:
- Skill CUD: registry.rs create/update/delete + serialize_skill_md + kernel proxy
- Workflow CUD: pipeline_commands.rs create/update/delete + serde_yaml依赖
- Agent更新: registry update方法 + AgentConfigUpdated事件 + agent_update命令
- Hand流式事件: HandStart/HandEnd变体替换ToolStart/ToolEnd
- 后端验证: hand_get/hand_run_status/hand_run_list确认实现完整
- Approval闭环: respond_to_approval后台spawn+5分钟超时轮询

P2/P3 质量改进:
- Browser WebDriver: TCP探测ChromeDriver/GeckoDriver/Edge端口替换硬编码true
- api-fallbacks: 移除假技能和16个捏造安全层，替换为真实能力映射
- dead_code清理: 移除5个模块级#![allow(dead_code)]，删除3个真正死方法，
  删除未注册的compactor_compact_llm命令，warnings从8降到3
- 所有变更通过cargo check + tsc --noEmit验证

crates/zclaw-skills/src/registry.rs

@@ -171,6 +171,150 @@ impl SkillRegistry {
         skills.insert(manifest.id.clone(), skill);
         manifests.insert(manifest.id.clone(), manifest);
     }
+
+    /// Create a skill from manifest, writing SKILL.md to disk
+    pub async fn create_skill(
+        &self,
+        skills_dir: &std::path::Path,
+        manifest: SkillManifest,
+    ) -> Result<()> {
+        let skill_dir = skills_dir.join(manifest.id.as_str());
+        if skill_dir.exists() {
+            return Err(zclaw_types::ZclawError::InvalidInput(
+                format!("Skill directory already exists: {}", skill_dir.display())
+            ));
+        }
+
+        // Create directory
+        std::fs::create_dir_all(&skill_dir)
+            .map_err(|e| zclaw_types::ZclawError::StorageError(
+                format!("Failed to create skill directory: {}", e)
+            ))?;
+
+        // Write SKILL.md
+        let content = serialize_skill_md(&manifest);
+        std::fs::write(skill_dir.join("SKILL.md"), &content)
+            .map_err(|e| zclaw_types::ZclawError::StorageError(
+                format!("Failed to write SKILL.md: {}", e)
+            ))?;
+
+        // Load into registry
+        self.load_skill_from_dir(&skill_dir).await?;
+
+        Ok(())
+    }
+
+    /// Update a skill manifest, rewriting SKILL.md on disk
+    pub async fn update_skill(
+        &self,
+        skills_dir: &std::path::Path,
+        id: &SkillId,
+        updates: SkillManifest,
+    ) -> Result<SkillManifest> {
+        // Find existing skill directory
+        let skill_dir = skills_dir.join(id.as_str());
+        if !skill_dir.exists() {
+            return Err(zclaw_types::ZclawError::NotFound(
+                format!("Skill directory not found: {}", skill_dir.display())
+            ));
+        }
+
+        // Merge: start from existing manifest, apply updates
+        let existing = self.get_manifest(id).await
+            .ok_or_else(|| zclaw_types::ZclawError::NotFound(
+                format!("Skill not found in registry: {}", id)
+            ))?;
+
+        let updated = SkillManifest {
+            id: existing.id.clone(),
+            name: if updates.name.is_empty() { existing.name } else { updates.name },
+            description: if updates.description.is_empty() { existing.description } else { updates.description },
+            version: if updates.version.is_empty() { existing.version } else { updates.version },
+            author: updates.author.or(existing.author),
+            mode: existing.mode,
+            capabilities: if updates.capabilities.is_empty() { existing.capabilities } else { updates.capabilities },
+            input_schema: updates.input_schema.or(existing.input_schema),
+            output_schema: updates.output_schema.or(existing.output_schema),
+            tags: if updates.tags.is_empty() { existing.tags } else { updates.tags },
+            category: updates.category.or(existing.category),
+            triggers: if updates.triggers.is_empty() { existing.triggers } else { updates.triggers },
+            enabled: updates.enabled,
+        };
+
+        // Rewrite SKILL.md
+        let content = serialize_skill_md(&updated);
+        std::fs::write(skill_dir.join("SKILL.md"), &content)
+            .map_err(|e| zclaw_types::ZclawError::StorageError(
+                format!("Failed to write SKILL.md: {}", e)
+            ))?;
+
+        // Reload into registry
+        self.remove(id).await;
+        self.load_skill_from_dir(&skill_dir).await?;
+
+        Ok(updated)
+    }
+
+    /// Delete a skill: remove directory from disk and unregister
+    pub async fn delete_skill(
+        &self,
+        skills_dir: &std::path::Path,
+        id: &SkillId,
+    ) -> Result<()> {
+        let skill_dir = skills_dir.join(id.as_str());
+        if skill_dir.exists() {
+            std::fs::remove_dir_all(&skill_dir)
+                .map_err(|e| zclaw_types::ZclawError::StorageError(
+                    format!("Failed to remove skill directory: {}", e)
+                ))?;
+        }
+
+        self.remove(id).await;
+        Ok(())
+    }
+}
+
+/// Serialize a SkillManifest into SKILL.md frontmatter format
+fn serialize_skill_md(manifest: &SkillManifest) -> String {
+    let mut parts = Vec::new();
+
+    // Frontmatter
+    parts.push("---".to_string());
+    parts.push(format!("name: \"{}\"", manifest.name));
+    parts.push(format!("description: \"{}\"", manifest.description));
+    parts.push(format!("version: \"{}\"", manifest.version));
+    parts.push(format!("mode: {}", match manifest.mode {
+        SkillMode::PromptOnly => "prompt-only",
+        SkillMode::Python => "python",
+        SkillMode::Shell => "shell",
+        SkillMode::Wasm => "wasm",
+        SkillMode::Native => "native",
+    }));
+    if !manifest.capabilities.is_empty() {
+        parts.push(format!("capabilities: {}", manifest.capabilities.join(", ")));
+    }
+    if !manifest.tags.is_empty() {
+        parts.push(format!("tags: {}", manifest.tags.join(", ")));
+    }
+    if !manifest.triggers.is_empty() {
+        parts.push("triggers:".to_string());
+        for trigger in &manifest.triggers {
+            parts.push(format!("  - \"{}\"", trigger));
+        }
+    }
+    if let Some(ref cat) = manifest.category {
+        parts.push(format!("category: \"{}\"", cat));
+    }
+    parts.push(format!("enabled: {}", manifest.enabled));
+    parts.push("---".to_string());
+    parts.push(String::new());
+
+    // Body: use description as the skill content
+    parts.push(format!("# {}", manifest.name));
+    parts.push(String::new());
+    parts.push(manifest.description.clone());
+
+    parts.join("\n")
 }
 
 impl Default for SkillRegistry {