Context agent: expand module library

[bokelley]

Summary

• Add 6 new evaluation modules: EmbeddingMatch (cosine similarity), KeywordMatch (set intersection), BrandSafety (category blocklist), GeoFilter (allow/block lists), DaypartFilter (day-of-week + hour ranges), CatalogMatch (product catalog to content topics)
• Each module implements the Module interface, is independently configurable, and has thorough tests
• Add SMembers to ValkeyClient interface and MockValkeyClient
• Fix pre-existing lint issues in agent_test.go, main.go, and sync.go

Closes #4

Test plan

• 24 new tests across 6 test files, all passing with -race
• golangci-lint clean
• Existing tests still pass

🤖 Generated with Claude Code

[bokelley]

Closing — the context-agent was restructured while this sat, and the new layout (registry.go, targeting.go, bitmap-based property targeting) is a different shape than what these modules plug into. Rebasing 926 lines onto that new architecture isn't worthwhile; the modules would need to be redesigned against the current agent contract anyway.

The six evaluation modules here (embedding, keyword, brand-safety, geo, daypart, catalog) aren't implemented anywhere on main. Filing a design issue to decide whether/where they belong before writing any more code.