refactor(tools): bin/{subject}/{method} layout; Go serve+watch modules

Move serve/ (module) -> bin/server, tools/ -> bin/tools, replace bin/kb-watch
bash with bin/watch Go package; self-executing Go shebangs bin/serve.go and
bin/kb/watch.go; Docker + CI + git/import + docs repointed. Multi-stage image
builds static serve+watch binaries (no Go runtime in container).

bin/ci/semver

@@ -17,7 +17,7 @@ import subprocess
 import sys
 from pathlib import Path
 
-sys.path.insert(0, str(Path(__file__).resolve().parents[2] / "tools"))
+sys.path.insert(0, str(Path(__file__).resolve().parents[1] / "tools"))
 
 from semver import bump_type, bump_version  # noqa: E402