JetBrains AI Assistant Rules File for Svelte app (50+ engineer scale-up)

You are a senior principal engineer with extensive technical knowledge in developer tooling. You write clear, precise, and implementation-ready content.

You are generating a rules/instructions file for JetBrains AI Assistant to steer AI coding assistants on a Svelte app codebase.

**Tool:** JetBrains AI Assistant
**Project:** Svelte app
**Team context:** 50+ engineer scale-up
**Non-negotiable convention:** SQL migrations must be reversible
**Primary test framework:** Rust cargo test + insta
**Primary language:** Go

## Your task
Write one complete, ready-to-save rules file. Pick the correct filename for JetBrains AI Assistant:
- Cursor -> `.cursorrules` (root) or `.cursor/rules/<scope>.mdc` with YAML frontmatter (`description`, `globs`, `alwaysApply`)
- GitHub Copilot -> `.github/copilot-instructions.md`
- Claude Code -> `CLAUDE.md` at repo root (and optionally `~/.claude/CLAUDE.md` for user-level)
- Windsurf -> `.windsurfrules`
- Aider -> `CONVENTIONS.md` (loaded via `aider --read CONVENTIONS.md`)
- Zed -> `.rules`
- Continue.dev -> `.continue/config.yaml` `systemMessage` block
- OpenAI Codex / generic -> `AGENTS.md`

Output the final file content verbatim inside a single fenced code block, with the filename as the first line of a header comment. No commentary before or after.

## Required sections (every file must include all)

### 1. Project Overview
- One paragraph describing the Svelte app and its purpose
- Stack summary: language, framework, database, deploy target
- Critical entrypoints (e.g. `app/page.tsx`, `cmd/server/main.go`, `src/main.py`)
- Directory map for the top 6-10 folders with one-line purposes

### 2. Coding Standards (the rules)
- Hard rule: SQL migrations must be reversible
- 8-12 additional enforceable rules written as imperatives ("always", "never", "prefer")
- Each rule must be checkable without running code
- Bias toward negative rules ("never use `any`") over positive ones

### 3. Testing
- Test runner: Rust cargo test + insta
- File naming convention (`*.test.ts`, `*_test.go`, `test_*.py`)
- What requires tests (every new public function / every bug fix / every route)
- How to run the full suite and a single file
- Coverage floor if the team enforces one

### 4. Forbidden Patterns
- Concrete anti-patterns with a one-line example of the wrong code
- Framework-specific footguns for Svelte app
- At least 5 items

### 5. Preferred Libraries
- Canonical choice for: HTTP client, logger, validator, date handling, ORM/DB, UI primitives
- For each: one line on why, and the wrong choice it replaces

### 6. Commit & PR Hygiene
- Conventional commits format with examples
- Max diff size per commit
- What goes in the PR description

### 7. When You Are Unsure
- Instruction to ask before: schema migrations, dependency additions, API contract changes, anything touching auth/billing
- Instruction to prefer reading the existing code over inventing new patterns

## Style of the file itself
- ~80-150 lines total
- Markdown, hierarchical headings
- No filler, no apologies, no "as an AI..."
- Every rule must be specific enough that a reviewer could reject a PR citing it
- For Cursor `.mdc` scoped rules, include accurate frontmatter:
  ```
  ---
  description: <one line>
  globs: <comma-separated glob patterns>
  alwaysApply: <true|false>
  ---
  ```

- Use precise technical terminology appropriate for the audience
- Include code examples, configurations, or specifications where relevant
- Document assumptions, prerequisites, and dependencies
- Provide error handling and edge case considerations

Provide a ready-to-use template with placeholder markers {{like_this}} that the user can fill in. Include instructions for each placeholder.