chore: scaffold mosaic monorepo (Phase 0)

- pnpm workspaces + Turborepo
- tsconfig.base.json strict ESM
- @mosaic/types stub package
- Woodpecker CI pipeline with Valkey service
- docs/PRD.md, docs/TASKS.md, CONTEXT.md

prettier.config.js

@@ -0,0 +1 @@
+export default { semi: true, singleQuote: true, trailingComma: 'all', printWidth: 100 };