feat(kb): brain tools, Go async serve, root-level docker

- tools/kblib.py: ladybug schema, embeddings, FTS+vector, hybrid RRF
- bin/kb/{index,search,get,stats,eval}: corpus indexing + deduction search
- bin/facts/{extract,audit}: 2-source evidence acquisition + gates
- serve/: async Go HTTP server (goroutines, bounded worker pool), TDD
- docker/ flattened to root: compose.yaml + Dockerfile (multi-stage Go)
- docker scripts -> bin/ shebang pattern (kb-watch, docker-entrypoint)
- bin/ci/semver + tools/semver.py: conventional-commit semver release
- ci.yml: go tests + shell checks; drop release-please (PR toggle blocked)

.dockerignore

@@ -0,0 +1,14 @@
+# .dockerignore - keep the build context lean.
+.venv
+var
+.git
+.github
+__pycache__
+*.pyc
+*.lbug
+*.lbug.*
+.cache
+.secrets
+.skills-tmp
+serve/serve
+docs/.build