Default password hashing to bcrypt (fits varchar(64) users.password)

Verified against the live AtomCMS DB: users.password is varchar(64), so
argon2id (~97 chars) overflows the column and registration/upgrade fail
with 'value too long'. bcrypt (60-char $2y$) fits and matches the
existing accounts. hashPassword() now emits bcrypt by default; set
PASSWORD_HASH=argon2id to opt back in (needs a widened column).
verifyPassword() still accepts both, so existing logins keep working.

Verified end-to-end against the live DB: bcrypt $2y$ login round-trips
(correct=true, wrong=false). tsc 0, vitest 8/8 (password suite).

src/lib/auth/password.ts

@@ -1,30 +1,51 @@
 import { createHash, randomBytes } from "node:crypto";
-import { compare as bcryptCompare } from "bcryptjs";
+import { compare as bcryptCompare, hash as bcryptHash } from "bcryptjs";
 import { argon2id, argon2Verify } from "hash-wasm";
 
-// AtomCMS hashing (config/hashing.php): default driver argon2id with
-// memory=65536 KiB, time=4, threads=1; bcrypt rounds=12 as the legacy fallback.
-// The game emulator validates the SAME users.password hash, so these must match.
+// AtomCMS hashing (config/hashing.php): argon2id with memory=65536 KiB, time=4,
+// threads=1; bcrypt rounds=12 as the legacy fallback. The game emulator
+// validates the SAME users.password hash, so these must match.
 const ARGON2_PARAMS = {
   parallelism: 1,
   iterations: 4,
   memorySize: 65536, // KiB
   hashLength: 32,
 } as const;
+const BCRYPT_ROUNDS = 12;
+
+// Which algorithm hashPassword() emits for NEW/upgraded passwords.
+//   - "bcrypt"  (DEFAULT): 60-char $2y$ hash. Fits a varchar(64) users.password
+//     (the common emulator/AtomCMS column width) and matches existing accounts.
+//   - "argon2id": ~97-char PHC hash. ONLY usable if users.password is widened
+//     (e.g. varchar(255)). Opt in with PASSWORD_HASH=argon2id.
+// verifyPassword() always accepts BOTH, so logins keep working either way.
+function hashDriver(): "bcrypt" | "argon2id" {
+  return process.env.PASSWORD_HASH?.toLowerCase() === "argon2id" ? "argon2id" : "bcrypt";
+}
 
 /** Lowercase hex md5 of a UTF-8 string (matches PHP md5()). */
 export function md5Hex(input: string): string {
   return createHash("md5").update(input, "utf8").digest("hex");
 }
 
-/** Produce an argon2id hash in PHC format identical to PHP's PASSWORD_ARGON2ID. */
+/**
+ * Hash a new password with the configured driver. Defaults to bcrypt ($2y$,
+ * rounds=12) so the result fits a varchar(64) column; set PASSWORD_HASH=argon2id
+ * for argon2id (requires a wider column). Both are verifiable by verifyPassword.
+ */
 export async function hashPassword(password: string): Promise<string> {
-  return argon2id({
-    password,
-    salt: randomBytes(16),
-    outputType: "encoded",
-    ...ARGON2_PARAMS,
-  });
+  if (hashDriver() === "argon2id") {
+    return argon2id({
+      password,
+      salt: randomBytes(16),
+      outputType: "encoded",
+      ...ARGON2_PARAMS,
+    });
+  }
+  // bcryptjs emits $2a$/$2b$; normalise to the PHP-canonical $2y$ the emulator
+  // and existing AtomCMS rows use.
+  const h = await bcryptHash(password, BCRYPT_ROUNDS);
+  return h.replace(/^\$2[ab]\$/, "$2y$");
 }
 
 /** True when `stored` is exactly the md5 of `password` (legacy AtomCMS accounts). */