fix(ui): address review feedback on chat infra slice

- export.ts: handle array content blocks (Claude API format) instead
  of silently exporting empty strings
- slash-command-executor.ts: restrict /kill all to current session's
  subagent subtree instead of all sessions globally
- slash-command-executor.ts: only count truly aborted runs (check
  aborted !== false) in /kill summary

ui/src/ui/chat/slash-command-executor.ts

@@ -296,9 +296,14 @@ async function executeKill(
     }
 
     const results = await Promise.allSettled(
-      matched.map((key) => client.request("chat.abort", { sessionKey: key })),
+      matched.map((key) =>
+        client.request<{ aborted?: boolean }>("chat.abort", { sessionKey: key }),
+      ),
     );
-    const successCount = results.filter((entry) => entry.status === "fulfilled").length;
+    const successCount = results.filter(
+      (entry) =>
+        entry.status === "fulfilled" && (entry.value as { aborted?: boolean })?.aborted !== false,
+    ).length;
     if (successCount === 0) {
       const firstFailure = results.find((entry) => entry.status === "rejected");
       throw firstFailure?.reason ?? new Error("abort failed");
@@ -343,15 +348,16 @@ function resolveKillTargets(
     }
     const normalizedKey = key.toLowerCase();
     const parsed = parseAgentSessionKey(normalizedKey);
+    // For "all", only match subagents belonging to the current session's agent
+    const belongsToCurrentSession =
+      currentParsed?.agentId != null && parsed?.agentId === currentParsed.agentId;
     const isMatch =
-      normalizedTarget === "all" ||
+      (normalizedTarget === "all" && belongsToCurrentSession) ||
       normalizedKey === normalizedTarget ||
       (parsed?.agentId ?? "") === normalizedTarget ||
       normalizedKey.endsWith(`:subagent:${normalizedTarget}`) ||
       normalizedKey === `subagent:${normalizedTarget}` ||
-      (currentParsed?.agentId != null &&
-        parsed?.agentId === currentParsed.agentId &&
-        normalizedKey.endsWith(`:subagent:${normalizedTarget}`));
+      (belongsToCurrentSession && normalizedKey.endsWith(`:subagent:${normalizedTarget}`));
     if (isMatch) {
       keys.add(key);
     }