fix: replace corrupted bytes and respect remote default branch

Replace broken control characters and U+FFFD replacement characters in
log function labels with ASCII equivalents ([ok], [!], [x]).

Drop the hardcoded "main" default for git_ref so arty deps no longer
fails with "pathspec 'main' did not match" on repos whose default branch
is not named main — git clone already checks out the remote default branch.
A ref: value in arty.yml is still honoured when explicitly set.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/arty.sh

@@ -47,15 +47,15 @@ log_info() {
 }
 
 log_success() {
-  echo -e "${GREEN}[]${NC} $1" >&2
+  echo -e "${GREEN}[ok]${NC} $1" >&2
 }
 
 log_warn() {
-  echo -e "${YELLOW}[�]${NC} $1" >&2
+  echo -e "${YELLOW}[!]${NC} $1" >&2
 }
 
 log_error() {
-  echo -e "${RED}[]${NC} $1" >&2
+  echo -e "${RED}[x]${NC} $1" >&2
 }
 
 log_debug() {
@@ -65,7 +65,7 @@ log_debug() {
 }
 
 log_step() {
-  echo -e "${CYAN}[�]${NC} $1" >&2
+  echo -e "${CYAN}[!]${NC} $1" >&2
 }
 
 # ============================================================================
@@ -403,7 +403,7 @@ is_installed() {
 install_lib() {
   local repo_url="$1"
   local lib_name="${2:-$(get_lib_name "$repo_url")}"
-  local git_ref="${3:-main}"
+  local git_ref="${3:-}"
   local custom_into="${4:-}"
   local config_file="${5:-$ARTY_CONFIG_FILE}"
 
@@ -453,9 +453,15 @@ install_lib() {
     fi
 
     # Try to update
-    (cd "$lib_dir" && git fetch -q && git checkout -q "$git_ref" && git pull -q) || {
-      log_warn "Failed to update library (continuing with existing version)"
-    }
+    if [[ -n "$git_ref" ]]; then
+      (cd "$lib_dir" && git fetch -q && git checkout -q "$git_ref" && git pull -q) || {
+        log_warn "Failed to update library (continuing with existing version)"
+      }
+    else
+      (cd "$lib_dir" && git fetch -q && git pull -q) || {
+        log_warn "Failed to update library (continuing with existing version)"
+      }
+    fi
 
     return 0
   fi
@@ -469,11 +475,11 @@ install_lib() {
 
   log_info "Installing library: $lib_name"
   log_info "Repository: $repo_url"
-  log_info "Git ref: $git_ref"
+  log_info "Git ref: ${git_ref:-<default>}"
   log_info "Location: $lib_dir"
 
   if [[ "$ARTY_DRY_RUN" == "1" ]]; then
-    log_info "[DRY RUN] Would clone repository and checkout $git_ref"
+    log_info "[DRY RUN] Would clone repository${git_ref:+ and checkout $git_ref}"
     unmark_installing "$lib_id_with_path"
     return 0
   fi
@@ -485,10 +491,12 @@ install_lib() {
     return 1
   }
 
-  # Checkout the specified ref
-  (cd "$lib_dir" && git checkout -q "$git_ref") || {
-    log_warn "Failed to checkout ref '$git_ref', using default branch"
-  }
+  # Checkout the specified ref (skip if none given; clone already checked out the default branch)
+  if [[ -n "$git_ref" ]]; then
+    (cd "$lib_dir" && git checkout -q "$git_ref") || {
+      log_warn "Failed to checkout ref '$git_ref', using default branch"
+    }
+  fi
 
   # Run setup hook if exists
   if [[ -f "$lib_dir/setup.sh" ]]; then
@@ -626,9 +634,6 @@ install_references() {
       continue
     fi
 
-    # Use default ref if not specified
-    [[ -z "$git_ref" ]] && git_ref="main"
-
     # Get library name
     local lib_name=$(get_lib_name "$url")
 
@@ -775,12 +780,12 @@ build_reference_tree() {
 
     # Add dirty indicator
     if [[ "$is_dirty" == "1" ]]; then
-      printf " ${YELLOW}${NC}"
+      printf " ${YELLOW}*${NC}"
     fi
 
     # Add location info
     if [[ -n "$into" ]]; then
-      printf " ${MAGENTA}� %s${NC}" "$into"
+      printf " ${MAGENTA}-> %s${NC}" "$into"
     fi
 
     echo
@@ -1748,7 +1753,7 @@ PROJECT DISCOVERY:
      tools/
          deep/
              nested/
-                 arty.yml   Too deep (>2 levels)
+                                   arty.yml   Too deep (>2 levels)
 
 ERROR HANDLING:
     - Individual project failures don't stop the batch