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>

builder/build-iso.sh

@@ -172,11 +172,16 @@ cp "${base_pkg_lists[1]}" "$build_cache_dir/airootfs/usr/share/omarchy-iso/omarc
 # disagree. A runtime predating the split ships no such file, which would leave
 # the configurator with no prompts at all.
 if [[ ! -f $setup_form ]]; then
-  echo "ERROR: $OMARCHY_RUNTIME_PACKAGE does not ship install/provisioning/setup-form.sh" >&2
+  if [[ -d /omarchy-source ]]; then
+    echo "ERROR: the --local-source checkout ships no install/provisioning/setup-form.sh" >&2
+    remedy="Update the checkout to a revision carrying the shared setup form."
+  else
+    echo "ERROR: $OMARCHY_RUNTIME_PACKAGE does not ship install/provisioning/setup-form.sh" >&2
+    remedy="Publish a runtime carrying the shared setup form, or build with --local-source against a checkout that has it."
+  fi
   echo "       The configurator sources its prompts from that file, so this ISO" >&2
   echo "       would boot into an installer with no questions to ask." >&2
-  echo "       Publish a runtime carrying the shared setup form, or build with" >&2
-  echo "       --local-source against a checkout that has it." >&2
+  echo "       $remedy" >&2
   exit 1
 fi
 cp "$setup_form" "$build_cache_dir/airootfs/usr/share/omarchy-iso/setup-form.sh"

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 $?