fix: complete vault layout transition — fs_path everywhere, no more spaces/

- notes.Create(): .md files stored in parent node's fs_path folder
- files.CopyIntoVault/CreateEmptyFile/Duplicate: use parent fs_path
- files.AddPathCopy/AddPathLink: use parent fs_path, set folder fs_path
- files.DeleteNodeAndChildren: move physical folder to .verstak/trash
- UpdateFsPathRecursive: use SafeDisplayNameToPathSegment(child.Title)
- sync_apply.go note ops: use fs_path instead of spaces/
- internal/gui/server.go file upload: use n.FsPath instead of nodeSlug
- VaultCheck diagnostic: walk nodes/files, verify paths on disk
- Tests: create/rename/move/delete/name-conflict/vault-check all pass

internal/core/notes/note.go

@@ -9,6 +9,7 @@ import (
 	"verstak/internal/core/files"
 	"verstak/internal/core/nodes"
 	"verstak/internal/core/storage"
+	"verstak/internal/core/templates"
 	"verstak/internal/core/util"
 )
 
@@ -40,33 +41,43 @@ func (s *Service) Create(parentID, title, section string) (*nodes.Node, *files.R
 		return nil, nil, fmt.Errorf("create node: %w", err)
 	}
 
-	slug := node.Slug
-	if slug == "" {
-		slug = "note"
+	seg := templates.SafeDisplayNameToPathSegment(title)
+	if seg == "" {
+		seg = "note"
+	}
+	filename := seg + ".md"
+
+	var destDir string
+	if parentID != "" {
+		parent, err := s.nodes.GetActive(parentID)
+		if err == nil && parent.FsPath != "" {
+			destDir = filepath.Join(s.vaultRoot, parent.FsPath)
+		}
+	}
+	if destDir == "" {
+		destDir = s.vaultRoot
+	}
+
+	if err := os.MkdirAll(destDir, 0o750); err != nil {
+		return nil, nil, fmt.Errorf("mkdir: %w", err)
 	}
-	filename := slug + ".md"
-	destDir := filepath.Join(s.vaultRoot, "spaces")
-	os.MkdirAll(destDir, 0o750)
 
 	dest := filepath.Join(destDir, filename)
 	if _, err := os.Stat(dest); err == nil {
-		filename = fmt.Sprintf("%s_%s.md", slug, node.ID[:8])
+		filename = fmt.Sprintf("%s_%s.md", seg, node.ID[:8])
 		dest = filepath.Join(destDir, filename)
 	}
 
-	// Write initial content.
 	if err := os.WriteFile(dest, []byte("# "+title+"\n\n"), 0o640); err != nil {
 		return nil, nil, fmt.Errorf("write: %w", err)
 	}
 
-	// Register file record.
 	relPath, _ := filepath.Rel(s.vaultRoot, dest)
 	fileRec, err := insertFileRecord(s.db, node.ID, filename, relPath, "vault", 0)
 	if err != nil {
 		return nil, nil, fmt.Errorf("insert file: %w", err)
 	}
 
-	// Link.
 	_, err = s.db.Exec(
 		`INSERT INTO notes (node_id, file_id, format) VALUES (?,?,?)`,
 		node.ID, fileRec.ID, "markdown")

internal/core/notes/note_test.go

@@ -49,11 +49,16 @@ func TestCreateAndRead(t *testing.T) {
 		t.Errorf("content = %q", content)
 	}
 
-	// Verify file on disk.
-	spacesDir := filepath.Join(vaultRoot, "spaces")
-	entries, _ := os.ReadDir(spacesDir)
-	if len(entries) == 0 {
-		t.Error("expected file in spaces/")
+	// Verify file on disk (in vault root for parentless notes).
+	entries, _ := os.ReadDir(vaultRoot)
+	var mdFiles int
+	for _, e := range entries {
+		if !e.IsDir() && filepath.Ext(e.Name()) == ".md" {
+			mdFiles++
+		}
+	}
+	if mdFiles == 0 {
+		t.Error("expected .md file in vault root")
 	}
 }