[Commerce] Add Etsy store management brief from imported sales evidence

[Nickel85]

Goal

Generate an interaction-first Etsy store management brief from imported orders and order items so the user can ask what to improve next.

Brief Should Include

• Sales summary.
• Top listings.
• Weak or stagnant listings.
• Bundle opportunities.
• Deal/coupon recommendations.
• Ad candidate recommendations.
• Data quality warnings.
• Decisions needing user review.

Acceptance Criteria

• Runs from imported CSV data without requiring Etsy API access.
• Uses deterministic analytics facts first, then optional LLM narration for explanation and prioritization.
• Shows clear evidence for each recommendation.
• Marks recommendations as draft/review-only.
• Produces next actions the user can accept, defer, reject, or log for later testing.
• Includes tests for no imports, partial imports, order-only imports, item-only imports, and complete imports.

[Nickel85]

Shared memory alignment note:

#164 now defines Mongoose as the shared agent memory provider. This issue should use the Mongoose memory provider for durable decision, preference, experiment, performance, and outcome records instead of creating an isolated agent-specific memory store.

Domain-specific logic can stay here, but storage/query/audit semantics should align with #164.