🛠️ REFACTOR: Remove custom type definitions for getLeavesOfType

## Issue
Redefining Obsidian's exposed types is redundant and can cause conflicts.

## Solution
Remove custom type definitions for `getLeavesOfType` and use built-in types.

## Priority
Medium - Code quality improvement

## Acceptance Criteria
- [ ] Custom type definitions removed
- [ ] Built-in types used
- [ ] TypeScript compilation works