Merge origin/main into fix/tunnel-traversal (conflict-only)

Conflict in ingestion/internal/brainfs/brainfs_test.go only: both sides
appended a test after TestReadRegularNeverReturnsAnInBrainFileSwappedInBehindASymlink
(this branch: TestWriteRegularRefusesFinalSymlinksFIFOsEscapesAndMissingFilesAndRewritesRegularFiles;
main: TestReadDirDirsListsOnlyRealSubdirsAndRefusesSymlinkedComponents).
Kept both, unchanged. No production code touched by the resolution.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ingestion/internal/brainfs/brainfs_test.go

@@ -308,3 +308,21 @@ func TestWriteRegularRefusesFinalSymlinksFIFOsEscapesAndMissingFilesAndRewritesR
 	got, _ = os.ReadFile(filepath.Join(dir, "n.md"))
 	assert.Equal(t, "new", string(got), "truncated and rewritten")
 }
+
+func TestReadDirDirsListsOnlyRealSubdirsAndRefusesSymlinkedComponents(t *testing.T) {
+	dir := t.TempDir()
+	require.NoError(t, os.MkdirAll(filepath.Join(dir, "a", "real"), 0o755))
+	require.NoError(t, os.MkdirAll(filepath.Join(dir, "other"), 0o755))
+	require.NoError(t, os.Symlink(filepath.Join("..", "other"), filepath.Join(dir, "a", "linked")))
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "a", "f.md"), []byte("f"), 0o644))
+	require.NoError(t, os.Symlink("a", filepath.Join(dir, "alias")))
+	b, err := Open(dir)
+	require.NoError(t, err)
+	defer func() { _ = b.Close() }()
+
+	names, err := b.ReadDirDirs("a")
+	require.NoError(t, err)
+	assert.Equal(t, []string{"real"}, names)
+	_, err = b.ReadDirDirs("alias")
+	assert.ErrorIs(t, err, ErrNotRegular)
+}