feat: add automatic word count and link validation to write operations

Add automatic word count and link validation to create_note, update_note,
and update_sections operations to provide immediate feedback on note content
quality and link integrity.

Features:
- Word counting excludes frontmatter and Obsidian comments, includes all
  other content (code blocks, inline code, headings, lists, etc.)
- Link validation checks wikilinks, heading links, and embeds
- Results categorized as: valid links, broken notes (note doesn't exist),
  and broken headings (note exists but heading missing)
- Detailed broken link info includes line number and context snippet
- Human-readable summary (e.g., "15 links: 12 valid, 2 broken notes, 1 broken heading")
- Opt-out capability via validateLinks parameter (default: true) for
  performance-critical operations

Implementation:
- New ContentUtils.countWords() for word counting logic
- Enhanced LinkUtils.validateLinks() for comprehensive link validation
- Updated create_note, update_note, update_sections to return wordCount
  and linkValidation fields
- Updated MCP tool descriptions to document new features and parameters
- update_note now returns structured JSON instead of simple success message

Response format changes:
- create_note: added wordCount and linkValidation fields
- update_note: changed to structured response with wordCount and linkValidation
- update_sections: added wordCount and linkValidation fields

Breaking changes:
- update_note response format changed from simple message to structured JSON

src/tools/note-tools-factory.ts

@@ -2,6 +2,7 @@ import { App } from 'obsidian';
 import { NoteTools } from './note-tools';
 import { VaultAdapter } from '../adapters/vault-adapter';
 import { FileManagerAdapter } from '../adapters/file-manager-adapter';
+import { MetadataCacheAdapter } from '../adapters/metadata-cache-adapter';
 
 /**
  * Factory function to create NoteTools with concrete adapters
@@ -10,6 +11,7 @@ export function createNoteTools(app: App): NoteTools {
 	return new NoteTools(
 		new VaultAdapter(app.vault),
 		new FileManagerAdapter(app.fileManager),
+		new MetadataCacheAdapter(app.metadataCache),
 		app
 	);
 }