refactor(security): unify hardened install and fs write flows

src/agents/skills-install-tar-verbose.ts

@@ -0,0 +1,80 @@
+const TAR_VERBOSE_MONTHS = new Set([
+  "Jan",
+  "Feb",
+  "Mar",
+  "Apr",
+  "May",
+  "Jun",
+  "Jul",
+  "Aug",
+  "Sep",
+  "Oct",
+  "Nov",
+  "Dec",
+]);
+const ISO_DATE_PATTERN = /^\d{4}-\d{2}-\d{2}$/;
+
+function mapTarVerboseTypeChar(typeChar: string): string {
+  switch (typeChar) {
+    case "l":
+      return "SymbolicLink";
+    case "h":
+      return "Link";
+    case "b":
+      return "BlockDevice";
+    case "c":
+      return "CharacterDevice";
+    case "p":
+      return "FIFO";
+    case "s":
+      return "Socket";
+    case "d":
+      return "Directory";
+    default:
+      return "File";
+  }
+}
+
+function parseTarVerboseSize(line: string): number {
+  const tokens = line.trim().split(/\s+/).filter(Boolean);
+  if (tokens.length < 6) {
+    throw new Error(`unable to parse tar verbose metadata: ${line}`);
+  }
+
+  let dateIndex = tokens.findIndex((token) => TAR_VERBOSE_MONTHS.has(token));
+  if (dateIndex > 0) {
+    const size = Number.parseInt(tokens[dateIndex - 1] ?? "", 10);
+    if (!Number.isFinite(size) || size < 0) {
+      throw new Error(`unable to parse tar entry size: ${line}`);
+    }
+    return size;
+  }
+
+  dateIndex = tokens.findIndex((token) => ISO_DATE_PATTERN.test(token));
+  if (dateIndex > 0) {
+    const size = Number.parseInt(tokens[dateIndex - 1] ?? "", 10);
+    if (!Number.isFinite(size) || size < 0) {
+      throw new Error(`unable to parse tar entry size: ${line}`);
+    }
+    return size;
+  }
+
+  throw new Error(`unable to parse tar verbose metadata: ${line}`);
+}
+
+export function parseTarVerboseMetadata(stdout: string): Array<{ type: string; size: number }> {
+  const lines = stdout
+    .split("\n")
+    .map((line) => line.trim())
+    .filter(Boolean);
+  return lines.map((line) => {
+    const typeChar = line[0] ?? "";
+    if (!typeChar) {
+      throw new Error("unable to parse tar entry type");
+    }
+    return {
+      type: mapTarVerboseTypeChar(typeChar),
+      size: parseTarVerboseSize(line),
+    };
+  });
+}