Bootstrap initial Copilot instructions

[danielgerlag]

This pull request adds comprehensive GitHub Copilot instruction files for each major project area in the Drasi platform monorepo. These instructions provide technology stack overviews, project structures, development guidelines, and common tasks for contributors working on CLI, control planes, query containers, sources, and reactions. The documentation is tailored to each subproject's language and architecture, helping developers follow best practices and maintain consistency across the codebase.

Project-specific Copilot instructions:

• .github/instructions/cli.md: Introduces development guidelines for the Go-based CLI, including project structure, build/test commands, error handling, and configuration management.
• .github/instructions/control-planes.md: Details Rust-based control plane services, covering architecture, API endpoints, error handling, async patterns, MongoDB integration, Dapr communication, and testing strategies.
• .github/instructions/query-container.md: Describes the Rust query container workspace, its services, build/test/lint workflow, and workspace management practices.
• .github/instructions/sources.md: Outlines how to develop new source connectors, including service patterns, SDK usage, debugging, optimization, and cloud authentication for Azure/AWS.
• .github/instructions/reactions.md: Explains how to build reaction components in various stacks (C#, TypeScript, etc.), with instructions for integration, error handling, cloud authentication, and debugging.

Monorepo-wide guidance:

• .github/instructions/instructions.md: Adds a high-level overview of the Drasi platform architecture, repository structure, build system, general development principles, documentation standards, and common commands for contributors.