feat: add adapter interfaces for dependency injection

Create IVaultAdapter, IMetadataCacheAdapter, and IFileManagerAdapter
interfaces to decouple tool classes from Obsidian API dependencies.

src/adapters/interfaces.ts

@@ -0,0 +1,53 @@
+import { TAbstractFile, TFile, TFolder, CachedMetadata, DataWriteOptions } from 'obsidian';
+
+/**
+ * Adapter interface for Obsidian Vault operations
+ */
+export interface IVaultAdapter {
+	// File reading
+	read(file: TFile): Promise<string>;
+
+	// File existence and metadata
+	stat(file: TAbstractFile): { ctime: number; mtime: number; size: number } | null;
+
+	// File retrieval
+	getAbstractFileByPath(path: string): TAbstractFile | null;
+	getMarkdownFiles(): TFile[];
+
+	// Directory operations
+	getRoot(): TFolder;
+
+	// File creation (process method)
+	process(file: TFile, fn: (data: string) => string, options?: DataWriteOptions): Promise<string>;
+
+	// Folder creation
+	createFolder(path: string): Promise<void>;
+
+	// File creation
+	create(path: string, data: string): Promise<TFile>;
+}
+
+/**
+ * Adapter interface for Obsidian MetadataCache operations
+ */
+export interface IMetadataCacheAdapter {
+	// Cache access
+	getFileCache(file: TFile): CachedMetadata | null;
+
+	// Link resolution
+	getFirstLinkpathDest(linkpath: string, sourcePath: string): TFile | null;
+
+	// File cache for links and metadata
+	resolvedLinks: Record<string, Record<string, number>>;
+	unresolvedLinks: Record<string, Record<string, number>>;
+}
+
+/**
+ * Adapter interface for Obsidian FileManager operations
+ */
+export interface IFileManagerAdapter {
+	// File operations
+	renameFile(file: TAbstractFile, newPath: string): Promise<void>;
+	trashFile(file: TAbstractFile): Promise<void>;
+	processFrontMatter(file: TFile, fn: (frontmatter: any) => void): Promise<void>;
+}