Remove Serena config, update gitignore, and add Claude Code setup docs

Author: kurosame

.gitignore

@@ -1,6 +1,4 @@
-.serena/cache/
-.serena/memories/
-.serena/.gitignore
+.serena/
 .DS_Store
 .env
 .vscode/*.log

.serena/project.yml

@@ -10,6 +10,7 @@
     "hashicorp",
     "hasura",
     "joho",
+    "kiro",
     "kurosame",
     "rssapp",
     "secretmanager",

.vscode/settings.json

@@ -66,3 +66,23 @@ The following resources are not supported by Terraform
 So create it from the GCP Console
 
 - Create a Datastore entity
+
+## Setup for Claude Code
+
+Execute the following command.
+
+```sh
+ln -s ~/ghq/github.com/kurosame/dotfiles/.claude/.mcp.json .
+
+npx cc-sdd@latest --lang ja # generate .claude/commands/kiro
+
+claude # Start Claude Code
+
+/init                    # generate CLAUDE.md
+/mcp__serena__onboarding # generate .serena
+/kiro:steering           # generate .kiro/steering
+
+codex # Start Codex
+
+/init # generate AGENTS.md
+```