chore: reorganize documentation and add gemini automation context

[DanilRostov]

Description

This PR reorganizes the project documentation and introduces a GEMINI.md file to improve AI-assisted development workflows.

Changes:

• Moved Documentation: Relocated rendering-related Markdown files (RENDERING_CONTROLS.md, RENDERING_PIPELINE_OVERVIEW.md, RENDERING_PIPELINE_TECHNICAL.md) from the root directory to the docs/ folder for better project structure.
• Added Gemini Context: Created GEMINI.md at the root to provide essential project context and GitHub CLI automation instructions for Gemini CLI.
• Repository Update: Ensured documentation reflects the project's current structure.

Motivation:

• Keep the root directory clean by grouping documentation.
• Enable more efficient issue management and automation using the gh CLI.

Verified that files are correctly placed in the docs/ directory.