refactor(agent): dedupe harness and command workflows

src/agents/skills-install-output.ts

@@ -0,0 +1,40 @@
+export type InstallCommandResult = {
+  code: number | null;
+  stdout: string;
+  stderr: string;
+};
+
+function summarizeInstallOutput(text: string): string | undefined {
+  const raw = text.trim();
+  if (!raw) {
+    return undefined;
+  }
+  const lines = raw
+    .split("\n")
+    .map((line) => line.trim())
+    .filter(Boolean);
+  if (lines.length === 0) {
+    return undefined;
+  }
+
+  const preferred =
+    lines.find((line) => /^error\b/i.test(line)) ??
+    lines.find((line) => /\b(err!|error:|failed)\b/i.test(line)) ??
+    lines.at(-1);
+
+  if (!preferred) {
+    return undefined;
+  }
+  const normalized = preferred.replace(/\s+/g, " ").trim();
+  const maxLen = 200;
+  return normalized.length > maxLen ? `${normalized.slice(0, maxLen - 1)}…` : normalized;
+}
+
+export function formatInstallFailureMessage(result: InstallCommandResult): string {
+  const code = typeof result.code === "number" ? `exit ${result.code}` : "unknown exit";
+  const summary = summarizeInstallOutput(result.stderr) ?? summarizeInstallOutput(result.stdout);
+  if (!summary) {
+    return `Install failed (${code})`;
+  }
+  return `Install failed (${code}): ${summary}`;
+}