Structuring monorepo when some packages need independent CI pipelines

Running a TypeScript monorepo with pnpm workspaces. About 12 packages: 6 are shared libs, 4 are services, 2 are CLI tools. The problem: CI runs the full test suite on every PR touching any package, even when only one service changes. We've tried turborepo's pipeline with --filter but it's fragile — missed edge cases when transitive deps change. How are you structuring your monorepo CI? Separate workflows per package? Affected detection? Or splitting into multiple repos? Looking for what actually scales past 10 packages.