feat(ingestion): symlink tripwire for the Syncthing-shared brain dir (#157) (#159)

Co-authored-by: Mathias <mthbqv@gmail.com>

ingestion/cmd/server/main.go

@@ -33,6 +33,7 @@ import (
 	"github.com/mathiasbq/hyperguild/ingestion/internal/reranker"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/search"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/startupretry"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/symlinkguard"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/vectorstore"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/watcher"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/webhook"
@@ -173,7 +174,8 @@ func alertingWarnings(getenv func(string) string) []string {
 	var out []string
 	if getenv("BRAIN_NTFY_URL") == "" {
 		out = append(out, "alerting DISABLED: BRAIN_NTFY_URL unset — "+
-			"brain_edit_root governance rewrites and capture audit degradation will not notify")
+			"brain_edit_root governance rewrites, capture audit degradation and the "+
+			"brain symlink tripwire (hyperguild#157) will not notify")
 	}
 	return out
 }
@@ -239,6 +241,10 @@ func main() {
 	}
 
 	brainDir := envOr("INGEST_BRAIN_DIR", "../brain")
+	if err := startupSymlinkCheck(brainDir); err != nil {
+		logger.Error("brain symlink tripwire", "err", err)
+		os.Exit(1)
+	}
 	port := envOr("INGEST_PORT", "3300")
 
 	llmURL := envOr("INGEST_LLM_URL", "http://iguana:4000/v1")
@@ -360,6 +366,8 @@ func main() {
 	}
 
 	ctx := context.Background()
+	// hyperguild#157: report a symlink that appears in the brain while running.
+	go symlinkguard.Watch(ctx, brainDir, symlinkScanInterval(os.Getenv), buildNotifier())
 
 	// Built before the watcher, the graph backfill and session ingestion, and
 	// retried rather than fatal (#83). Two separate reasons: