Redesign wizard UI with gum (charmbracelet)

- Bootstrap gum automatically on first run (Arch/Debian/RHEL/Fedora/SUSE)
- utils.sh: replace all bash color helpers with gum equivalents
  - gum input for text prompts (with value pre-fill for defaults)
  - gum choose for selection menus
  - gum confirm for yes/no
  - gum spin for long-running operations
  - gum style/log for output (catppuccin mocha palette)
  - gum style for banners and summary box
- core.sh: spinner on git clone/pull
- workflow.sh: spinner on git clone
- prereqs.sh: spinner on package installs
- wizard.sh: double-border welcome banner, rounded summary box,
  success banner with next-steps panel

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

lib/workflow.sh

@@ -12,7 +12,7 @@ generate_workflow() {
     local preset="$5"
     local workflow_dir="$project_dir/workflow"
 
-    info "Generating workflow config ($preset preset)..."
+    info "Generating workflow ($preset preset)..."
 
     mkdir -p "$workflow_dir/agents"
     mkdir -p "$workflow_dir/roles"
@@ -111,7 +111,7 @@ Read \`project-docs/project-vision.md\` for project goals.
 Use \`/sm <agent> "message"\` to send messages between agents.
 EOF
 
-    success "Workflow generated at $workflow_dir"
+    success "Workflow generated"
 }
 
 _create_agent_dir() {
@@ -159,8 +159,8 @@ clone_workflow() {
     local repo_url="$2"
     local workflow_dir="$project_dir/workflow"
 
-    info "Cloning workflow from $repo_url..."
-    git clone "$repo_url" "$workflow_dir" \
+    spin "Cloning workflow..." \
+        git clone "$repo_url" "$workflow_dir" \
         || die "Failed to clone workflow repo: $repo_url"
-    success "Workflow cloned to $workflow_dir"
+    success "Workflow cloned"
 }