test(me): add integration tests for gitlab_base_url in robot JSON envelope

Guards against regression in the wiring chain run_me -> print_me_json ->
MeJsonEnvelope where the gitlab_base_url meta field could silently
disappear.

- me_envelope_includes_gitlab_base_url_in_meta: verifies full envelope
  serialization preserves the base URL in meta
- activity_event_carries_url_construction_fields: verifies activity events
  contain entity_type + entity_iid + project fields, then demonstrates
  URL construction by combining with meta.gitlab_base_url

src/cli/commands/me/render_robot.rs

@@ -479,4 +479,107 @@ mod tests {
         assert_eq!(value["data"]["cursor_reset"], serde_json::json!(true));
         assert_eq!(value["meta"]["elapsed_ms"], serde_json::json!(17));
     }
+
+    /// Integration test: full envelope serialization includes gitlab_base_url in meta.
+    /// Guards against drift where the wiring from run_me -> print_me_json -> JSON
+    /// could silently lose the base URL field.
+    #[test]
+    fn me_envelope_includes_gitlab_base_url_in_meta() {
+        let dashboard = MeDashboard {
+            username: "testuser".to_string(),
+            since_ms: Some(1_700_000_000_000),
+            summary: MeSummary {
+                project_count: 1,
+                open_issue_count: 0,
+                authored_mr_count: 0,
+                reviewing_mr_count: 0,
+                mentioned_in_count: 0,
+                needs_attention_count: 0,
+            },
+            open_issues: vec![],
+            open_mrs_authored: vec![],
+            reviewing_mrs: vec![],
+            mentioned_in: vec![],
+            activity: vec![],
+            since_last_check: None,
+        };
+
+        let envelope = MeJsonEnvelope {
+            ok: true,
+            data: MeDataJson::from_dashboard(&dashboard),
+            meta: RobotMeta::with_base_url(42, "https://gitlab.example.com"),
+        };
+
+        let value = serde_json::to_value(&envelope).unwrap();
+        assert_eq!(value["ok"], serde_json::json!(true));
+        assert_eq!(value["meta"]["elapsed_ms"], serde_json::json!(42));
+        assert_eq!(
+            value["meta"]["gitlab_base_url"],
+            serde_json::json!("https://gitlab.example.com")
+        );
+    }
+
+    /// Verify activity events carry the fields needed for URL construction
+    /// (entity_type, entity_iid, project) so consumers can combine with
+    /// meta.gitlab_base_url to build links.
+    #[test]
+    fn activity_event_carries_url_construction_fields() {
+        let dashboard = MeDashboard {
+            username: "testuser".to_string(),
+            since_ms: Some(1_700_000_000_000),
+            summary: MeSummary {
+                project_count: 1,
+                open_issue_count: 0,
+                authored_mr_count: 0,
+                reviewing_mr_count: 0,
+                mentioned_in_count: 0,
+                needs_attention_count: 0,
+            },
+            open_issues: vec![],
+            open_mrs_authored: vec![],
+            reviewing_mrs: vec![],
+            mentioned_in: vec![],
+            activity: vec![MeActivityEvent {
+                timestamp: 1_700_000_000_000,
+                event_type: ActivityEventType::Note,
+                entity_type: "mr".to_string(),
+                entity_iid: 99,
+                project_path: "group/repo".to_string(),
+                actor: Some("alice".to_string()),
+                is_own: false,
+                summary: "Commented on MR".to_string(),
+                body_preview: None,
+            }],
+            since_last_check: None,
+        };
+
+        let envelope = MeJsonEnvelope {
+            ok: true,
+            data: MeDataJson::from_dashboard(&dashboard),
+            meta: RobotMeta::with_base_url(0, "https://gitlab.example.com"),
+        };
+
+        let value = serde_json::to_value(&envelope).unwrap();
+        let event = &value["data"]["activity"][0];
+
+        // These three fields + meta.gitlab_base_url = complete URL
+        assert_eq!(event["entity_type"], "mr");
+        assert_eq!(event["entity_iid"], 99);
+        assert_eq!(event["project"], "group/repo");
+
+        // Consumer constructs: https://gitlab.example.com/group/repo/-/merge_requests/99
+        let base = value["meta"]["gitlab_base_url"].as_str().unwrap();
+        let project = event["project"].as_str().unwrap();
+        let entity_path = match event["entity_type"].as_str().unwrap() {
+            "issue" => "issues",
+            "mr" => "merge_requests",
+            other => panic!("unexpected entity_type: {other}"),
+        };
+        let iid = event["entity_iid"].as_i64().unwrap();
+        let url = format!("{base}/{project}/-/{entity_path}/{iid}");
+        assert_eq!(
+            url,
+            "https://gitlab.example.com/group/repo/-/merge_requests/99"
+        );
+    }
 }