test(protocols,skills): add 90 tests for MCP types + skill loader/runner

zclaw-protocols: +43 tests covering mcp_types serde, ContentBlock
variants, transport config builders, and domain type roundtrips.

zclaw-skills: +47 tests covering SKILL.md/TOML parsing, auto-classify,
PromptOnlySkill execution, and SkillManifest/SkillResult roundtrips.

Batch 8 of audit plan (plans/stateless-petting-rossum.md).

crates/zclaw-skills/tests/runner_tests.rs

@@ -0,0 +1,78 @@
+//! Tests for PromptOnlySkill runner
+
+use zclaw_skills::*;
+use zclaw_types::SkillId;
+
+/// Helper to create a minimal manifest
+fn test_manifest(mode: SkillMode) -> SkillManifest {
+    SkillManifest {
+        id: SkillId::new("test-prompt-skill"),
+        name: "Test Prompt Skill".to_string(),
+        description: "A test prompt skill".to_string(),
+        version: "1.0.0".to_string(),
+        author: None,
+        mode,
+        capabilities: vec![],
+        input_schema: None,
+        output_schema: None,
+        tags: vec![],
+        category: None,
+        triggers: vec![],
+        tools: vec![],
+        enabled: true,
+    }
+}
+
+#[tokio::test]
+async fn prompt_only_skill_returns_formatted_prompt() {
+    let manifest = test_manifest(SkillMode::PromptOnly);
+    let template = "Hello {{input}}, welcome!".to_string();
+    let skill = PromptOnlySkill::new(manifest, template);
+
+    let ctx = SkillContext::default();
+    let skill_ref: &dyn Skill = &skill;
+    let result = skill_ref.execute(&ctx, serde_json::json!("World")).await.unwrap();
+
+    assert!(result.success);
+    let output = result.output.as_str().unwrap();
+    assert_eq!(output, "Hello World, welcome!");
+}
+
+#[tokio::test]
+async fn prompt_only_skill_json_input() {
+    let manifest = test_manifest(SkillMode::PromptOnly);
+    let template = "Input: {{input}}".to_string();
+    let skill = PromptOnlySkill::new(manifest, template);
+
+    let ctx = SkillContext::default();
+    let input = serde_json::json!({"key": "value"});
+    let skill_ref: &dyn Skill = &skill;
+    let result = skill_ref.execute(&ctx, input).await.unwrap();
+
+    assert!(result.success);
+    let output = result.output.as_str().unwrap();
+    assert!(output.contains("key"));
+    assert!(output.contains("value"));
+}
+
+#[tokio::test]
+async fn prompt_only_skill_no_placeholder() {
+    let manifest = test_manifest(SkillMode::PromptOnly);
+    let template = "Static prompt content".to_string();
+    let skill = PromptOnlySkill::new(manifest, template);
+
+    let ctx = SkillContext::default();
+    let skill_ref: &dyn Skill = &skill;
+    let result = skill_ref.execute(&ctx, serde_json::json!("ignored")).await.unwrap();
+
+    assert!(result.success);
+    assert_eq!(result.output.as_str().unwrap(), "Static prompt content");
+}
+
+#[tokio::test]
+async fn prompt_only_skill_manifest() {
+    let manifest = test_manifest(SkillMode::PromptOnly);
+    let skill = PromptOnlySkill::new(manifest.clone(), "prompt".to_string());
+    assert_eq!(skill.manifest().id.as_str(), "test-prompt-skill");
+    assert_eq!(skill.manifest().name, "Test Prompt Skill");
+}