Add config.json setup hint to install script

Users had no way to discover config.json for precise token counting
unless they ran `stats` and noticed the hint. Now the installer prints
setup instructions after install, and ships a config.json.template
in the repo for reference.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0192twUPgNxmFCpvpsBk5uqg

Author: Mapleeeeeeeeeee

config.json.template

@@ -0,0 +1,3 @@
+{
+  "anthropic_api_key_file": "~/.config/anthropic/.env"
+}

install.sh

@@ -182,6 +182,12 @@ print_next_steps() {
   echo "  cc-session read <id>     # 讀取對話內容"
   echo "  /cc-session              # 在 Claude Code 中使用 (需已安裝 Skill)"
   echo ""
+  echo "── Token counting (optional) ──────────────────────────────────────"
+  echo "  For precise token counts in 'cc-session stats', create:"
+  echo "  $SKILL_DIR/config.json"
+  echo ""
+  echo '  {"anthropic_api_key_file": "<path-to-your-api-key-file>"}'
+  echo ""
 }
 
 main() {