Add comprehensive autocomplete support for Pro and Interactive modes

[bluemoonfoundry]

This commit implements intelligent autocomplete across both Pro Mode and Interactive Mode, with scene-aware suggestions from DAZ Studio.

Major Features:

• UI hints system for visual metaphors (sliders, spinners, dropdowns, file pickers)
• Scene cache manager with background polling (queries DAZ via Script Server)
• Pro Mode autocomplete using HTML5 datalists
• Interactive Mode autocomplete using prompt-toolkit with context awareness
• Type-filtered suggestions (cameras, lights, figures, props)
• Visual indicators (emoji icons) for node types
• Special commands (.refresh, .stats, .help) in Interactive Mode

Technical Changes:

• Added ui and autocomplete sections to config.yaml (22 commands, 70+ widgets)
• Created vangard/scene_cache.py - thread-safe cache with 30s polling
• Created vangard/interactive_completer.py - SmartCompleter with context parsing
• Enhanced vangard/interactive.py - styled prompts and special commands
• Enhanced vangard/pro.py - added 4 scene API endpoints and lifecycle hooks
• Updated vangard/server.py - pass metadata through OpenAPI schema
• Updated vangard/static/js/app.js - widget generation and autocomplete integration
• Updated vangard/static/css/styles.css - styling for new widgets

Documentation:

• UI_HINTS_IMPLEMENTATION.md - UI hints technical details
• UI_HINTS_TEST_CHECKLIST.md - UI hints testing guide
• SCENE_AUTOCOMPLETE_IMPLEMENTATION.md - scene cache architecture
• SCENE_AUTOCOMPLETE_QUICKSTART.md - user setup guide
• INTERACTIVE_AUTOCOMPLETE.md - interactive mode documentation
• INTERACTIVE_AUTOCOMPLETE_TEST.md - 37 test cases
• INTERACTIVE_MODE_SUMMARY.md - complete implementation summary
• Updated CLAUDE.md with new features and architecture