fix: resolve go lint findings

[marcus]

Summary

• handle current errcheck findings in runtime command paths so best-effort logging/focus updates no longer ignore errors
• clean up additional reproducible errcheck findings across tests and helpers, using focused fixes plus file-level test nolints where the setup would otherwise be repetitive noise
• preserve formatting-only updates from the current tree and fix the flaky in-memory SQLite assertion in internal/sync/events_test.go

Validation

• golangci-lint run ./...
• gofmt -l .
• go vet ./...
• go test ./...

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