bruno: replace Python generator with Go golden-writer in the drift test

The generator moves into the Go toolchain per repo preference:
internal/docs/bruno_gen.go emits the OpenCollection mirrors (same output
contract — gate-verified example-request bodies, env-var params,
device-token headers, login/register/refresh token-capture scripts) and
TestBrunoMirrorsDocs grows a -update flag: verification by default,
regeneration on demand:

  go test ./internal/docs -run TestBrunoMirrorsDocs -update

Generator and checker are now the same code — they cannot drift apart.
scripts/gen_bruno_from_docs.py deleted; opencollection.yml README points
at the go-test command.

Also fixed vs the Python pass: mirror placement follows the docs tree
folder (RelPath), not the area frontmatter (several docs — highlights,
notes, ratings, users, progress — carry a different area); docs blocks
emit the collection's mapping form (content + type), not a bare scalar;
JSON body sanity is checked at generation time.

Idempotent: back-to-back -update runs are byte-identical.
make test green (9 pkgs).

internal/docs/drift_test.go

@@ -3,6 +3,7 @@ package docs
 import (
 	"bytes"
 	"encoding/json"
+	"flag"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -189,16 +190,33 @@ func parseHandlerMiddleware(rest string) []string {
 // TestBrunoMirrorsDocs keeps the executable-verification layer honest:
 // every frontmatter'd endpoint doc must have a generated OpenCollection
 // (Bruno) request whose method and URL shape match. Bruno is regenerated
-// from the docs (scripts/gen_bruno_from_docs.py); if this test fails, the
-// collection drifted from the canonical docs or a new doc was added
-// without regenerating.
+// from the docs; if this test fails, the collection drifted from the
+// canonical docs or a new doc was added without regenerating.
+//
+// Regenerate with:  go test ./internal/docs -run TestBrunoMirrorsDocs -update
+var updateBruno = flag.Bool("update", false, "rewrite generated Bruno mirrors from the canonical docs")
+
 func TestBrunoMirrorsDocs(t *testing.T) {
-	docsDir := "../../docs/developer/api"
+	docsDir := docsRoot
 	docs, err := LoadAPIDocs(docsDir)
 	if err != nil {
 		t.Fatalf("walk %s: %v", docsDir, err)
 	}
 
+	if *updateBruno {
+		written, deleted, err := updateBrunoMirrors(docs)
+		if err != nil {
+			t.Fatalf("regenerate bruno mirrors: %v", err)
+		}
+		t.Logf("bruno mirrors: %d written, %d deleted", len(written), len(deleted))
+		for _, rel := range written {
+			t.Logf("  wrote %s", rel)
+		}
+		for _, rel := range deleted {
+			t.Logf("  deleted %s", rel)
+		}
+	}
+
 	// Collect bruno requests: "METHOD normalized-path" -> relpath.
 	bruno := map[string]string{}
 	files, _ := filepath.Glob("../../bruno/**/*.yml")
@@ -238,7 +256,7 @@ func TestBrunoMirrorsDocs(t *testing.T) {
 		path := regexp.MustCompile(`:[^/{}]+`).ReplaceAllString(doc.Frontmatter.Path, "{}")
 		key := doc.Frontmatter.Method + " " + path
 		if _, ok := bruno[key]; !ok {
-			t.Errorf("%s: no Bruno request mirrors %q — run scripts/gen_bruno_from_docs.py --apply", doc.RelPath, key)
+			t.Errorf("%s: no Bruno request mirrors %q — regenerate: go test ./internal/docs -run TestBrunoMirrorsDocs -update", doc.RelPath, key)
 		}
 	}
 }