processor: return error when markdown pre-scan cannot read .md

claimedByMarkdown now wraps os.ReadFile failures instead of skipping,
so Run fails fast and avoids wrong image claim state. Add regression
test using an unreadable markdown file (Unix).

Made-with: Cursor

1 files changed, 35 insertions, 0 deletions

diff --git a/internal/processor/markdown_test.go b/internal/processor/markdown_test.go
index a17b704..2445b53 100644
--- a/internal/processor/markdown_test.go
+++ b/internal/processor/markdown_test.go
@@ -3,7 +3,10 @@ package processor
 import (
 	"os"
 	"path/filepath"
+	"runtime"
 	"testing"
+
+	"codeberg.org/snonux/snonux/internal/config"
 )
 
 func TestFindLocalImages(t *testing.T) {
@@ -88,3 +91,35 @@ func TestFindLocalImages(t *testing.T) {
 		})
 	}
 }
+
+func TestRun_UnreadableMarkdownPreScanFails(t *testing.T) {
+	t.Parallel()
+	if runtime.GOOS == "windows" {
+		t.Skip("chmod does not reliably deny read for owned files on Windows")
+	}
+
+	base := t.TempDir()
+	inputDir := filepath.Join(base, "inbox")
+	outputDir := filepath.Join(base, "out")
+	if err := os.MkdirAll(inputDir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.MkdirAll(outputDir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+
+	mdPath := filepath.Join(inputDir, "note.md")
+	if err := os.WriteFile(mdPath, []byte("# x\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Chmod(mdPath, 0); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = os.Chmod(mdPath, 0o644) })
+
+	cfg := &config.Config{InputDir: inputDir, OutputDir: outputDir}
+	_, err := Run(cfg)
+	if err == nil {
+		t.Fatal("Run: expected error when markdown pre-scan cannot read a .md file")
+	}
+}