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.

README.md

@@ -121,8 +121,8 @@ bin/brain/search.go "invoice from last week"                            # same s
 
 `bin/{subject}/{method}.go` — self-describing: shebang on line 1, usage comment
 from line 2. Shared code in `internal/`. YAML default output, `--json` for
-machines. Tests gate every commit. HTTP: `bin/brain/serve.go` (default search
-binary `var/bin/brain-search`, not Python).
+machines. Tests gate every commit. HTTP: `bin/brain/serve.go` calls
+`internal/brain` in-process (`/health` `/search` `/get` `/stats` `/audit` `/ingest`).
 
 ## Development