Correct two misleading messages from the setup-form split

The build's missing-form error only ever described the published-package
case, so a --local-source build against a checkout without the form told
you to publish a runtime or pass --local-source — advice you had already
taken. Branch on /omarchy-source and name the checkout instead.

The password comment has claimed yescrypt since 880d8c5 swapped the
command to `openssl passwd -6`, which is SHA-512 crypt. openssl passwd
cannot produce yescrypt at all, so the comment, not the command, is what
was wrong.

Both spotted by Copilot's review on #104.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

configs/airootfs/root/configurator

@@ -252,7 +252,7 @@ user_form() {
   omarchy_prompt_username || return $?
   omarchy_prompt_password || return $?
 
-  # Hash the password using yescrypt
+  # Hash the password with SHA-512 crypt ($6$), which is what openssl passwd offers
   password_hash=$(printf '%s' "$password" | openssl passwd -6 -stdin)
 
   omarchy_prompt_identity || return $?