chore: replace all node/npm/tsx references with bun across codebase

- Source: setup/service.ts, runners.ts, agent-runner.ts error messages
- Scripts: restart-stack.sh, run-migrations.ts → bun
- Bootstrap: setup.sh check_node→check_bun, npm install→bun install
- Docs: CLAUDE.md, README.md, all SKILL.md files
- Tests: service.test.ts, restart-stack.test.ts expectations updated

scripts/restart-ejclaw-stack.sh

@@ -5,4 +5,4 @@ SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 PROJECT_ROOT="$(cd "${SCRIPT_DIR}/.." && pwd)"
 
 cd "${PROJECT_ROOT}"
-npx tsx setup/restart-stack.ts "$@"
+bun setup/restart-stack.ts "$@"