Move all development tools from tools/ to scripts/ for consistency.
Rename lint/fmt/check-fmt to lint-clj/fmt-clj/check-fmt-clj to clarify
they target Clojure specifically. Remove unused scripts (attach-opencode,
start-opencode, start-opencode-server) and the backport-commit skill.
Update all internal references across .serena/, AGENTS.md, and
CONTRIBUTING.md to point to the new script locations. Simplify
CONTRIBUTING.md by delegating module-specific fmt/lint instructions
to the respective serena memories.
AI-assisted-by: deepseek-v4-flash
