feat: align browser callback runtime and export flows

Consolidate the browser task runtime around the callback path, add safer artifact opening for Zhihu exports, and cover the new service/browser flows with focused tests and supporting docs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/browser_backend_capability_test.rs

@@ -0,0 +1,145 @@
+mod common;
+
+use std::collections::HashMap;
+use std::fs;
+use std::path::PathBuf;
+use std::sync::Arc;
+use std::time::{SystemTime, UNIX_EPOCH};
+
+use common::MockTransport;
+use sgclaw::browser::{BrowserBackend, PipeBrowserBackend};
+use sgclaw::compat::browser_script_skill_tool::build_browser_script_skill_tools;
+use sgclaw::pipe::{Action, CommandOutput, ExecutionSurfaceKind, ExecutionSurfaceMetadata};
+use sgclaw::security::MacPolicy;
+use zeroclaw::skills::{Skill, SkillTool};
+
+fn backend_policy() -> MacPolicy {
+    MacPolicy::from_json_str(
+        r#"{
+            "version": "1.0",
+            "domains": { "allowed": ["oa.example.com", "erp.example.com"] },
+            "pipe_actions": {
+                "allowed": ["click", "type", "navigate", "getText"],
+                "blocked": ["eval", "executeJsInPage"]
+            }
+        }"#,
+    )
+    .unwrap()
+}
+
+fn eval_policy() -> MacPolicy {
+    MacPolicy::from_json_str(
+        r#"{
+            "version": "1.0",
+            "domains": { "allowed": ["www.zhihu.com"] },
+            "pipe_actions": {
+                "allowed": ["click", "type", "navigate", "getText", "eval"],
+                "blocked": []
+            }
+        }"#,
+    )
+    .unwrap()
+}
+
+#[test]
+fn pipe_browser_backend_keeps_privileged_pipe_surface_metadata() {
+    let transport = Arc::new(MockTransport::new(vec![]));
+    let backend = PipeBrowserBackend::new(transport, backend_policy(), vec![1, 2, 3, 4]);
+
+    let metadata = backend.surface_metadata();
+
+    assert_eq!(metadata.kind, ExecutionSurfaceKind::PrivilegedBrowserPipe);
+    assert!(metadata.privileged);
+    assert!(!metadata.defines_runtime_identity);
+    assert_eq!(metadata.guard, "mac_policy");
+    assert_eq!(
+        metadata.allowed_domains,
+        vec!["oa.example.com", "erp.example.com"]
+    );
+    assert_eq!(
+        metadata.allowed_actions,
+        vec!["click", "type", "navigate", "getText"]
+    );
+}
+
+#[test]
+fn pipe_browser_backend_reports_eval_capability_from_mac_policy() {
+    let transport = Arc::new(MockTransport::new(vec![]));
+    let backend = PipeBrowserBackend::new(transport, eval_policy(), vec![1, 2, 3, 4]);
+
+    assert!(backend.supports_eval());
+}
+
+#[test]
+fn browser_script_tools_are_hidden_when_backend_cannot_eval() {
+    let skill_root = unique_temp_dir("sgclaw-browser-backend-capability");
+    let scripts_dir = skill_root.join("scripts");
+    fs::create_dir_all(&scripts_dir).unwrap();
+    fs::write(
+        scripts_dir.join("extract_hotlist.js"),
+        "return { rows: [[1, '标题', '10万热度']] };",
+    )
+    .unwrap();
+
+    let skills = vec![Skill {
+        name: "zhihu-hotlist".to_string(),
+        description: "Zhihu hotlist helpers".to_string(),
+        version: "1.0.0".to_string(),
+        author: None,
+        tags: vec![],
+        tools: vec![SkillTool {
+            name: "extract_hotlist".to_string(),
+            description: "Extract structured hotlist rows".to_string(),
+            kind: "browser_script".to_string(),
+            command: "scripts/extract_hotlist.js".to_string(),
+            args: HashMap::new(),
+        }],
+        prompts: vec![],
+        location: Some(skill_root.join("skill.json")),
+    }];
+    let backend: Arc<dyn BrowserBackend> = Arc::new(FakeBrowserBackend::new(false));
+
+    let tools = build_browser_script_skill_tools(&skills, backend).unwrap();
+
+    assert!(tools.is_empty());
+}
+
+#[derive(Default)]
+struct FakeBrowserBackend {
+    supports_eval: bool,
+}
+
+impl FakeBrowserBackend {
+    fn new(supports_eval: bool) -> Self {
+        Self { supports_eval }
+    }
+}
+
+impl BrowserBackend for FakeBrowserBackend {
+    fn invoke(
+        &self,
+        _action: Action,
+        _params: serde_json::Value,
+        _expected_domain: &str,
+    ) -> Result<CommandOutput, sgclaw::pipe::PipeError> {
+        panic!("invoke should not be called in this capability-gating test")
+    }
+
+    fn surface_metadata(&self) -> ExecutionSurfaceMetadata {
+        ExecutionSurfaceMetadata::privileged_browser_pipe("fake_backend")
+    }
+
+    fn supports_eval(&self) -> bool {
+        self.supports_eval
+    }
+}
+
+fn unique_temp_dir(prefix: &str) -> PathBuf {
+    let nanos = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap()
+        .as_nanos();
+    let path = std::env::temp_dir().join(format!("{prefix}-{nanos}"));
+    fs::create_dir_all(&path).unwrap();
+    path
+}