docs(readme): add Droid (Factory) to documentation

Add Droid (Factory) references to CLAUDE.md and README.md to match the code changes from dd12a70 (feat: add Droid (Factory) support).

CLAUDE.md:
- Add .factory/skills/ui-ux-pro-max/ to architecture diagram
- Add .factory/ to symlinks description in Sync Rules

README.md:
- Add 'uipro init --ai droid' to CLI installation commands
- Add Droid (Factory) to Skill Mode supported platforms list
- Add .factory/skills/ path note for design system commands
- Add .factory/ to platform-specific files list in Architecture section
- Add .factory/ to contributor structure overview

CLAUDE.md

@@ -52,6 +52,7 @@ cli/                              # CLI installer (uipro-cli on npm)
     └── templates/                # Copy of src/ui-ux-pro-max/templates/
 
 .claude/skills/ui-ux-pro-max/     # Claude Code skill (symlinks to src/)
+.factory/skills/ui-ux-pro-max/   # Droid (Factory) skill (symlinks to src/)
 .shared/ui-ux-pro-max/            # Symlink to src/ui-ux-pro-max/
 .claude-plugin/                   # Claude Marketplace publishing
 ```
@@ -67,7 +68,7 @@ When modifying files:
 1. **Data & Scripts** - Edit in `src/ui-ux-pro-max/`:
    - `data/*.csv` and `data/stacks/*.csv`
    - `scripts/*.py`
-   - Changes automatically available via symlinks in `.claude/`, `.shared/`
+   - Changes automatically available via symlinks in `.claude/`, `.factory/`, `.shared/`
 
 2. **Templates** - Edit in `src/ui-ux-pro-max/templates/`:
    - `base/skill-content.md` - Common SKILL.md content