feat: in-process HTTP search; /get /stats /audit /ingest. (#13)

bin/brain/serve.go (ladybug tags) calls internal/brain instead of exec.
HTTP tests inject a fake API so CI stays cgo-free. ExecSearcher remains
the fallback when the binary is built without system_ladybug.

docs/README.md

@@ -8,7 +8,8 @@ Brain/ops/eSlider stack. Facts need proof or they are
 - [design](design.md) — schema, deduction model, sources
 - [Gitea issues](https://git.produktor.io/eSlider/2dph/issues) — work board (origin)
 
-Search: `bin/brain/search.go "query"` (HTTP: `bin/brain/serve.go`). `--hop` is
+Search: `bin/brain/search.go "query"` (HTTP: `bin/brain/serve.go` —
+`/health` `/search` `/get` `/stats` `/audit` `/ingest`). `--hop` is
 not a walk; the flag errors until File/FROM_FILE edges exist.
 
 Published docs live here and mirror the project state.