Generate an opinionated Cursor ruleset for a Next.js App Router plus TS monorepo

You are a senior staff engineer who configures AI coding assistants to respect a codebase's conventions. Generate a complete, opinionated Cursor rules file.

Repo context:
- Monorepo tool: [Turborepo / Nx / pnpm workspaces]
- Package manager: [pnpm / npm / yarn]
- Next.js version: [14 / 15], App Router, TypeScript strict.
- Key packages: [LIST — e.g. 'apps/web (Next.js), apps/admin (Next.js), packages/ui, packages/db (Prisma), packages/config']
- Styling: [Tailwind / CSS Modules / styled-components]
- State / data: [Server Components by default / TanStack Query / Zustand]

Generate a single .cursorrules file (project rules) that is specific to THIS repo, not generic boilerplate. Cover at minimum:

1. Architecture map — the package layout, what lives where, and which package owns shared code.
2. App Router conventions — co-location rules, when to use Server vs Client Components, the 'use client' boundary, and where route handlers and server actions go.
3. TypeScript rules — strict mode, no implicit any, the types-vs-interfaces convention for this repo, no @ts-ignore without a comment.
4. Import rules — absolute imports via the configured path aliases, no deep cross-package relative imports, import ordering.
5. Data-fetching rules — prefer Server Components for reads, where mutations go, how to type Prisma/client payloads, no fetch in a client component when the server can do it.
6. Styling rules — the chosen system, token usage, no inline magic values, conditional className patterns.
7. Testing rules — the test framework, where tests live, what must be covered before a change is 'done'.
8. PR / commit rules — conventional commits, and what a complete change includes (types, tests, docs if the API changed).

Critical format rules:
- Every rule MUST be followed by a one-line 'Why:' rationale so the agent understands intent, not just the letter.
- Be opinionated and concrete to THIS stack. Ban the wrong patterns by name (e.g. no getServerSideProps in an App Router repo).
- Keep it under roughly 120 lines so it fits Cursor's context comfortably. No filler.

Output the full .cursorrules file in a single fenced code block, then a 5-bullet summary of the most important conventions it enforces.

Success signal: the output is good only if every rule has a rationale, the rules are specific to Next.js App Router and this monorepo layout (not copy-pasteable to a different stack), and the wrong-pattern bans are named explicitly.