Add Provider Strategist agent under root

[EightRice]

Goal

A permanent non-removable child of the orchestrator that researches the LLM provider landscape, surfaces cost-optimization recommendations, and maintains the _PROVIDER_MODELS catalog.

Responsibilities

• Run on a daily heartbeat.
• Watch for new model releases and pricing changes across known providers (Anthropic, OpenAI, Google, DeepSeek, others as they appear).
• Maintain atn/runtime/provider_manager.py:_PROVIDER_MODELS (and atn/model_specs.py context-window / max-output-tokens entries) by proposing PRs or local edits.
• Recommend which agents in the local subtree should switch providers based on current usage and pricing — surfaces recommendations via notify_parent, never acts unilaterally.
• Track subscription quotas (SDKRateLimitEvent snapshots already aggregated per-provider) and flag near-limit conditions.

Out of scope

• Making provider switches itself. The strategist recommends; root or user decides.
• Implementing EIT — that's a separate issue this strategist will eventually consume.

Acceptance

• The strategist appears under the root in the agent tree on every startup, cannot be removed via the standard remove-agent path.
• A heartbeat run produces at least one structured recommendation in a recognizable format.
• The snapshot shows when the strategist last ran and a digest of its findings.