[keyman] keep the passphrase off argv, and recover a missing .pub

Generate prompted for the passphrase itself and passed it as `-N <value>`,
so it sat in this process's argv — readable by any user on the box through
`ps` for the length of the spawn — and in keyman's memory before that.
Verified that omitting `-N` makes ssh-keygen prompt *and* confirm, so the
prompt and the flag are both gone and the spawn inherits stdio. keyman no
longer learns the passphrase, which is strictly better than handling it more
carefully, and it deletes code.

The other half is the missing `.pub`. The selection list is built from
private keys, so an orphan is offered like any other, and copyFileSync
discovered the absent sibling only *after* age had written the encrypted
key: a vault entry with no public key, and an exception that took the rest
of the batch with it. It is now derived with `ssh-keygen -y -f`, before the
vault directory is created. Verified against real binaries that the derived
key matches the original byte for byte, that an encrypted key prompts (on
stderr — hence stdout piped, stdin and stderr inherited), and that a refused
derivation degrades to storing the private key alone rather than failing.

encrypt's loop now isolates per key and reports which ones did not make it,
except for ToolNotFoundError: age missing is not a per-key problem and nine
more identical errors help nobody.

storeInVault is the shared write path both callers had a copy of. It also
undoes its own mess: age has to write into a directory that already exists,
so a failure could leave an empty directory or a truncated .age — which list
counts as a vault entry and decrypt offers. The .age is removed because we
named it, the directory only while empty, since one holding an earlier key
is not ours to delete.

packages/keyman/src/keyman.encrypt.ts

@@ -1,7 +1,8 @@
 import fs from 'node:fs';
 import path from 'node:path';
 import inquirer from 'inquirer';
-import { runTool } from './keyman.utils.js';
+import { ToolNotFoundError } from './keyman.utils.js';
+import { storeInVault } from './keyman.vault.js';
 
 /**
  * Private keys in a directory that may not exist.
@@ -35,17 +36,30 @@ export async function encryptKeys(sshDir: string, keysDir: string, tmpDir: strin
     },
   ]);
 
+  const failed: string[] = [];
+
   for (const key of selectedKeys) {
     const keyPath = path.join(tmpKeys.includes(key) ? tmpDir : sshDir, key);
-    const vaultPath = path.join(keysDir, key.replace('id_', ''));
-    fs.mkdirSync(vaultPath, { recursive: true, mode: 0o700 });
 
-    // Encrypt key using `age`
-    await runTool('age', ['-r', pubkey, '-o', path.join(vaultPath, `${key}.age`), keyPath]);
+    try {
+      await storeInVault(keyPath, keysDir, pubkey);
+    } catch (error) {
+      // One bad key costs one key. Selecting ten and losing the last nine to an
+      // unreadable first one was the old behaviour, and nothing afterwards said
+      // which of the ten had made it into the vault.
+      if (error instanceof ToolNotFoundError) {
+        // Not a per-key problem: age is missing for all of them, so nine more
+        // identical failures would tell the user nothing new.
+        throw error;
+      }
+      failed.push(key);
+      console.error(`❌ ${key}: ${error instanceof Error ? error.message : error}`);
+    }
+  }
 
-    // Copy public key and create README
-    fs.copyFileSync(`${keyPath}.pub`, path.join(vaultPath, `${key}.pub`));
-
-    console.log(`🔒 Encrypted and stored: ${vaultPath}/${key}`);
+  if (failed.length > 0) {
+    console.log(
+      `\n⚠️  ${failed.length} of ${selectedKeys.length} selected keys were not stored: ${failed.join(', ')}`
+    );
   }
 }