fix(zsxq): require active group context

[jackwener]

Summary

• require an active ZSXQ group context instead of silently falling back to the first joined group
• rename the helper to getActiveGroupId to match the new behavior
• add adapter tests for topics/search when no active group context exists

Verification

• npx vitest run --project adapter src/clis/zsxq/topic.test.ts src/clis/zsxq/topics.test.ts src/clis/zsxq/search.test.ts
• npm run typecheck