[Epic] Implement WAD Overlay/Profile Builder (ltk_overlay)

[Crauzer]

Overview

Create a shared Rust crate (ltk_overlay) that provides WAD overlay building functionality for both the CLI and GUI applications. This will enable incremental mod installation, cross-WAD matching, string overrides, and conflict resolution.

Context

The current overlay implementation exists only in ltk-manager and is tightly coupled to Tauri. We need to extract and enhance this functionality into a reusable library that can be shared across the toolkit.

Related Issues:

• Add string overrides support to modpkg format #84 - Add string overrides support to modpkg format (prerequisite)
• Implement UI flow for setting string overrides in workshop mod editor #83 - Implement UI flow for setting string overrides

Reference:

• Design doc: docs/overlay-builder-design.md
• Implementation plan: docs/overlay-implementation-plan.md
• Summary: docs/OVERLAY-SUMMARY.md

Timeline

~10 weeks - See implementation plan for details

Implementation Tracking

✅ Phase 1: Core Extraction (Weeks 1-2)

• [ltk_overlay][Phase 1] Create ltk_overlay crate structure #86 - Create ltk_overlay crate structure - COMPLETED
• Extract game indexing logic
• Extract WAD building logic
• Extract utility functions
• Implement main OverlayBuilder
• Update ltk-manager to use ltk_overlay

Phase 2: Incremental Rebuild (Weeks 3-4)

• Design and implement state persistence
• Implement fingerprinting system
• Implement incremental rebuild logic
• Add health check system

Phase 3: String Overrides (Weeks 5-6)

• #96 - Research and document string table format
• Add string overrides support to modpkg format #84 - Extend mod metadata schema
• Implement string override system #97 - Implement string override system

Phase 4: Enhanced Conflict Resolution (Week 7)

• Implement conflict detection #98 - Implement conflict detection

Phase 5: CLI Integration (Week 8)

• Add CLI commands for overlay management #99 - Add CLI commands for overlay management

Phase 6-7: Testing, Docs, Performance (Weeks 9-10)

• #100 - Add comprehensive tests
• Complete documentation for ltk_overlay #101 - Complete documentation
• Performance optimization and profiling #102 - Performance optimization and profiling

Success Criteria

• ltk_overlay crate compiles and works independently ✅ (Done)
• ltk-manager successfully migrated to use new crate
• Incremental rebuild shows measurable performance improvement
• String overrides work in-game
• Conflict detection provides clear information
• CLI commands functional and documented
• Test coverage > 80%
• All documentation complete

Notes

See detailed implementation tasks in the linked issues above. Phase 1 and Phase 2 detailed issues will be created as we progress through the work.

The crate scaffold is complete and compiles successfully. Next step is to begin extracting the core logic from ltk-manager.