docs: Comprehensive Single-Tab Navigation Refactor and Context Era Positioning

[EthanThatOneKid]

Overview

This PR represents a massive architectural rewrite of the Worlds documentation site, transitioning to a high-visibility, single-tab root layout while aggressively pruning legacy content. It aligns the platform's positioning with the 2026 "Context Era" and introduces strict new style guidelines.

Key Architectural Changes

• Unified Navigation: Eliminated complex nested tabs in favor of a streamlined, tab-less root layout with optimized group headers.
• Product Hierarchy: Introduced explicit nested tabs and group organization for the core Engine and Platform.
• Integrations Hub: Extracted 11 active AI frameworks (Claude, Gemini, CrewAI, Agno, etc.) into a dedicated integrations/ directory with native icons and connection guides.
• Component Upgrades: Replaced raw markdown lists with interactive CardGroup grids for feature discovery.

Content Consolidation

• Aggressive Pruning: Deleted outdated /academy, /contributing, and fragmented /overview pages.
• The Manifesto: Authored a cohesive manifesto.mdx tracking the philosophical transition from the Semantic Web to the active "Context Layer".
• The Whitepaper: Rewrote whitepaper.mdx to reflect hard 2026 GraphRAG KPIs (99% vs 20%), the "Universal World Engine" thesis, and Low-ETL interoperability.
• Style Guide: Introduced strict style.mdx rules enforcing objective, active-voice, and code-forward technical writing.