fix: harden Base manifest recovery

tools/select-manifest.mjs

@@ -1,4 +1,4 @@
-import { access, readFile, rename } from "node:fs/promises";
+import { link, readFile, rm } from "node:fs/promises";
 import { join, resolve } from "node:path";
 import { pathToFileURL } from "node:url";
 
@@ -14,7 +14,7 @@ export async function selectManifest({ root = process.cwd(), network }) {
   return { source, active };
 }
 
-export async function archiveManifest({ root = process.cwd(), network, now = new Date() }) {
+export async function archiveManifest({ root = process.cwd(), network, now = new Date(), io = {} }) {
   if (network !== "baseSepolia") throw new Error("only baseSepolia may be archived");
   const spec = networkSpec(network);
   const source = join(root, "deployments", spec.canonical);
@@ -23,16 +23,20 @@ export async function archiveManifest({ root = process.cwd(), network, now = new
   const timestamp = now.toISOString().replace(/[-:.]/g, "");
   if (!/^\d{8}T\d{9}Z$/.test(timestamp)) throw new Error("archive timestamp is invalid");
   const target = join(root, "deployments", `base-sepolia.${timestamp}.json`);
+  const operations = { link, rm, ...io };
   try {
-    await access(target);
+    await operations.link(source, target);
   } catch (error) {
-    if (error.code === "ENOENT") {
-      await rename(source, target);
-      return { source, path: target };
-    }
+    if (error.code === "EEXIST") throw new Error("refusing to overwrite an existing Base Sepolia archive");
     throw error;
   }
-  throw new Error("refusing to overwrite an existing Base Sepolia archive");
+  try {
+    await operations.rm(source);
+  } catch (error) {
+    await operations.rm(target, { force: true }).catch(() => {});
+    throw error;
+  }
+  return { source, path: target };
 }
 
 export async function runSelectCli(argv, { root = process.cwd(), log = console.log } = {}) {