feat: brain get/stats/eval call internal/brain, not Python (#18)

Read path is cgo like search. Control questions live in rank so CI can
test them without ladybug. Python bin/kb/{get,stats,eval} stays the
runner fallback.

bin/brain/eval.go

@@ -1,20 +1,22 @@
-//usr/bin/env go run -tags=brain_eval "$0" "$@"; exit
-//go:build brain_eval
+//usr/bin/env go run -tags=system_ladybug,brain_eval "$0" "$@"; exit
+//go:build cgo && system_ladybug && brain_eval
 //
 // bin/brain/eval.go - recall@5 gate.
 //
 //	./bin/brain/eval.go
 //	./bin/brain/eval.go --json
 //
+// Needs CGO + libladybug. Python bin/kb/eval is the CI fallback (no cgo).
+// Control questions live in internal/brain/rank (cgo-free).
 // NOTE: never run `gofmt -w` on this file — it breaks the shebang.
 package main
 
 import (
 	"os"
 
-	"github.com/eSlider/2dph/internal/cmdbin"
+	"github.com/eSlider/2dph/internal/brain"
 )
 
 func main() {
-	os.Exit(cmdbin.ExecFile("bin/kb/eval", os.Args[1:]))
+	os.Exit(brain.MainEval(os.Args[1:]))
 }

bin/brain/get.go

@@ -1,20 +1,22 @@
-//usr/bin/env go run -tags=brain_get "$0" "$@"; exit
-//go:build brain_get
+//usr/bin/env go run -tags=system_ladybug,brain_get "$0" "$@"; exit
+//go:build cgo && system_ladybug && brain_get
 //
 // bin/brain/get.go - read one leaf by id.
 //
 //	./bin/brain/get.go <id>
 //	./bin/brain/get.go <id> --body
+//	./bin/brain/get.go <id> --json
 //
+// Needs CGO + libladybug. Python bin/kb/get is the CI fallback (no cgo).
 // NOTE: never run `gofmt -w` on this file — it breaks the shebang.
 package main
 
 import (
 	"os"
 
-	"github.com/eSlider/2dph/internal/cmdbin"
+	"github.com/eSlider/2dph/internal/brain"
 )
 
 func main() {
-	os.Exit(cmdbin.ExecFile("bin/kb/get", os.Args[1:]))
+	os.Exit(brain.MainGet(os.Args[1:]))
 }

bin/brain/stats.go

@@ -1,20 +1,21 @@
-//usr/bin/env go run -tags=brain_stats "$0" "$@"; exit
-//go:build brain_stats
+//usr/bin/env go run -tags=system_ladybug,brain_stats "$0" "$@"; exit
+//go:build cgo && system_ladybug && brain_stats
 //
 // bin/brain/stats.go - index health.
 //
 //	./bin/brain/stats.go
 //	./bin/brain/stats.go --json
 //
+// Needs CGO + libladybug. Python bin/kb/stats is the CI fallback (no cgo).
 // NOTE: never run `gofmt -w` on this file — it breaks the shebang.
 package main
 
 import (
 	"os"
 
-	"github.com/eSlider/2dph/internal/cmdbin"
+	"github.com/eSlider/2dph/internal/brain"
 )
 
 func main() {
-	os.Exit(cmdbin.ExecFile("bin/kb/stats", os.Args[1:]))
+	os.Exit(brain.MainStats(os.Args[1:]))
 }

bin/tools/test_bin_layout.py

@@ -77,6 +77,37 @@ class BinLayoutTest(unittest.TestCase):
         for method in ("index.go", "get.go", "stats.go", "eval.go", "watch.go"):
             self._assert_shebang(f"bin/brain/{method}")
 
+    def test_brain_get_stats_eval_are_not_python_exec(self) -> None:
+        for method in ("get.go", "stats.go", "eval.go"):
+            text = (ROOT / "bin" / "brain" / method).read_text()
+            self.assertNotIn(
+                "ExecFile",
+                text,
+                f"bin/brain/{method} must call internal/brain, not ExecFile Python",
+            )
+            self.assertNotIn(
+                "cmdbin",
+                text,
+                f"bin/brain/{method} must not import internal/cmdbin",
+            )
+            self.assertIn(
+                "system_ladybug",
+                text.splitlines()[0],
+                f"bin/brain/{method} shebang must pass -tags=system_ladybug",
+            )
+            self.assertIn(
+                "github.com/eSlider/2dph/internal/brain",
+                text,
+            )
+
+    def test_eval_control_questions_live_in_rank(self) -> None:
+        rank = (ROOT / "internal" / "brain" / "rank" / "evalq.go").read_text()
+        py = (ROOT / "bin" / "kb" / "eval").read_text()
+        for frag in ("BM25", "DevOps", "LadybugDB"):
+            self.assertIn(frag, rank)
+            self.assertIn(frag, py)
+        self.assertIn("0.95", rank)
+
     def test_mail_import_is_shebang_not_brain_write(self) -> None:
         self._assert_shebang("bin/mail/import.go")
         index_mail = (ROOT / "bin" / "mail" / "index_mail").read_text()

bin/tools/test_published_docs.py

@@ -59,6 +59,14 @@ class PublishedDocsTest(unittest.TestCase):
         self.assertNotIn("password", settings.lower())
         self.assertIn("json", settings)
 
+    def test_readme_read_path_is_go(self) -> None:
+        plan = (ROOT / "PLAN.md").read_text()
+        self.assertIn("get.go", plan)
+        self.assertIn("CI fallback", plan)
+        design = (ROOT / "docs" / "design.md").read_text()
+        self.assertIn("internal/brain/rank", design)
+        self.assertIn("They do not exec Python", design)
+
     def test_readme_search_escalates_web(self) -> None:
         text = (ROOT / "README.md").read_text()
         self.assertIn("--no-web", text)