Fixes #5763

Problem

The index scanning feature was showing instantly green without actually performing the scan, particularly in Unity projects with hundreds of script files where the scan should take 10-15 minutes.

Root Cause

The issue was in the code indexing orchestrator where:

1. No proper progress reporting during file discovery phase
2. Missing validation of actual scanning work performed
3. Instant completion when all files were cached (no visual feedback)
4. State transitions to "Indexed" without confirming actual work was done

Solution

• Enhanced Progress Reporting: Added detailed progress messages during file discovery, filtering, and processing phases
• Work Validation: Added validation to ensure actual scanning work was performed before transitioning to "Indexed" state
• Meaningful Completion Messages: Provide specific feedback based on scan results (e.g., "All files were cached", "Processed X files and indexed Y blocks")
• Edge Case Handling: Proper handling when no files need processing or no supported files are found
• Interface Enhancement: Added progress callback to scanner interface for better user feedback

Changes

• src/services/code-index/orchestrator.ts: Enhanced progress reporting and work validation
• src/services/code-index/processors/scanner.ts: Added progress reporting during file discovery
• src/services/code-index/interfaces/file-processor.ts: Added progress callback to interface

Testing

• All existing tests pass
• Scanner tests: ✅ 7 passed
• Config manager tests: ✅ 72 passed
• Type checking: ✅ All packages pass
• Linting: ✅ All packages pass

The fix ensures users see proper progress feedback during scanning and prevents the misleading instant green status.