docs: documentation for user agents

[MgnMtn]

CLOSE #7

[Copilot]

Pull request overview

Adds a structured documentation set for humans and AI agents to work effectively in the multiplex repo, including an index, architecture/pipeline overview, configuration schema, module/function reference, extension checklists, and development/agent guidance (Issue #7).

Changes:

• Introduces docs/ documentation set (index + architecture, config, module reference, extending, development guides).
• Adds agent-focused entrypoints (AGENTS.md, CLAUDE.md) pointing to the task-scoped docs and common commands.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
docs/README.md	Index entrypoint for the new task-scoped documentation set.
docs/ARCHITECTURE.md	Describes end-to-end pipeline, approaches, backends, and artifacts.
docs/MODULE_REFERENCE.md	Function/signature-oriented reference for key modules.
docs/CONFIG.md	Documents config.yml schema and required keys.
docs/EXTENDING.md	Checklists for adding approaches, backends, and providers.
docs/DEVELOPMENT.md	Developer setup, conventions, CI notes, known issues.
AGENTS.md	Guidance and doc map for AI coding agents working in-repo.
CLAUDE.md	Claude Code-specific guidance and doc map for the repo.

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