docs: add production engineering contract for AI agents

[masarray]

Summary

Adds a repository-level AGENTS.md that makes production architecture, root-cause-first debugging, UI-thread safety, bounded data processing, lifecycle management, regression protection, measurable performance, Result-oriented failure handling, and asynchronous diagnostics part of the implementation contract for every AI/code agent.

Added failure architecture

• expected/recoverable hot-path failures use TryXxx / typed Result<T> / structured status instead of exception-driven control flow
• OS/.NET/library exceptions are contained at meaningful boundaries and converted to structured failures
• hot-path diagnostics enqueue compact machine-readable events only
• diagnostic queues must be bounded, deduplicated/rate-limited, and non-blocking to critical work
• diagnostic infrastructure is observational; logging failure must not become application failure

Why

ARSAS already has strong PR validation gates. This moves the same discipline earlier into reconnaissance, architecture, implementation, debugging, and failure handling so agents do not accumulate trial-and-error patches before validation.

Documentation-only change; no runtime behavior is modified.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Reverse the infrastructure dependency arrow

When an agent follows these arrows as the declared dependency direction, the diagram instructs the Domain layer to depend on Infrastructure, allowing engineering models/calculations to couple directly to file, network, device, or OS implementations. That reverses the service/adapter boundary described immediately below; Infrastructure adapters should instead depend inward on application/domain contracts rather than sit downstream of Domain.

AGENTS.md reference: AGENTS.md:L41-L46

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