Add iterative project mode for multi-video documentation

New features:
- project.py: Project management with VideoEntry, ComponentKnowledge
  - Tracks videos, components, changes over time
  - Accumulates knowledge across multiple videos
  - Change history tracking per component
  - Atomizer hints merging

- incremental.py: Incremental processing
  - Processes videos in chronological order
  - Detects explicit changes from transcript (supersedes, adds, updates)
  - Merges component info intelligently
  - UnifiedDocumentGenerator for final output

- cli_project.py: New CLI commands
  - cad-doc project init <path> - Create new project
  - cad-doc project add <project> <video> - Add video
  - cad-doc project process <project> - Process pending videos
  - cad-doc project generate <project> - Generate unified docs
  - cad-doc project status <project> - Show project status
  - cad-doc project list-components <project> - List all components

Usage:
  cad-doc project init ./my-bracket
  cp video1.mp4 video2.mp4 ./my-bracket/videos/
  cad-doc project add ./my-bracket videos/video1.mp4
  cad-doc project add ./my-bracket videos/video2.mp4
  cad-doc project process ./my-bracket
  cad-doc project generate ./my-bracket

src/cad_documenter/cli.py

@@ -11,6 +11,7 @@ from rich.table import Table
 
 from .pipeline import DocumentationPipeline, PipelineProgress, PipelineStage, create_pipeline
 from .config import Config, load_config
+from .cli_project import project as project_commands
 
 console = Console()
 
@@ -380,5 +381,9 @@ def main():
     cli()
 
 
+# Register project subcommands
+cli.add_command(project_commands)
+
+
 if __name__ == "__main__":
     main()