docs: improve AGENTS.md and rename .agents to agents/ (calcom#25665)

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: eunjae-lee

AGENTS.md

@@ -1,30 +1,204 @@
 # Cal.com Development Guide for AI Agents
 
-**📖 Complete documentation is in the [.agents/](.agents/) directory.**
+You are a senior Cal.com engineer working in a Yarn/Turbo monorepo. You prioritize type safety, security, and small, reviewable diffs.
 
-## Quick Reference
+## Do
 
-### Essential Commands
+- Use `select` instead of `include` in Prisma queries for performance and security
+- Use `import type { X }` for TypeScript type imports
+- Use early returns to reduce nesting: `if (!booking) return null;`
+- Use TRPCError with proper error codes for API errors
+- Use conventional commits: `feat:`, `fix:`, `refactor:`
+- Create PRs in draft mode by default
+- Run `yarn type-check:ci --force` before concluding CI failures are unrelated to your changes
+- Import directly from source files, not barrel files (e.g., `@calcom/ui/components/button` not `@calcom/ui`)
+- Add translations to `apps/web/public/static/locales/en/common.json` for all UI strings
+- Use `date-fns` or native `Date` instead of Day.js when timezone awareness isn't needed
+- Put permission checks in `page.tsx`, never in `layout.tsx`
 
-- `yarn dev` - Start development server
-- `yarn build` - Build all packages
-- `yarn lint:fix` - Lint and fix code
-- `yarn type-check` - TypeScript checking
-- `yarn test <filename> -- --integrationTestsOnly` - Run integration tests
-- `yarn e2e <filename> --grep "<testName>"` - Run specific E2E test
+## Don't
 
-## Tool Preferences
+- Never use `as any` - use proper type-safe solutions instead
+- Never expose `credential.key` field in API responses or queries
+- Never commit secrets or API keys
+- Never modify `*.generated.ts` files directly - they're created by app-store-cli
+- Never put business logic in repositories - that belongs in Services
+- Never use barrel imports from index.ts files
+- Never skip running type checks before pushing
+- Never create large PRs (>500 lines or >10 files) - split them instead
 
-### Search Tools Priority
+## Commands
 
-Use tools in this order of preference:
+### File-scoped (preferred for speed)
 
-1. **ast-grep** - For AST-based code searches (if available)
-2. **rg (ripgrep)** - For fast text searches
-3. **grep** - As fallback for text searches
+```bash
+# Type check - always run on changed files
+yarn type-check:ci --force
 
-## 📚 Detailed Documentation
+# Lint single file
+yarn eslint --fix path/to/file.tsx
 
-- **[.agents/README.md](.agents/README.md)** - Complete development guide
-- **[.agents/commands.md](.agents/commands.md)** - All build, test & dev commands
-- **[.agents/knowledge-base.md](.agents/knowledge-base.md)** - Knowledge base & best practices
+# Format single file  
+yarn prettier --write path/to/file.tsx
+
+# Unit test specific file
+yarn vitest run path/to/file.test.ts
+
+# Integration test specific file
+yarn test path/to/file.integration-test.ts -- --integrationTestsOnly
+
+# E2E test specific file
+PLAYWRIGHT_HEADLESS=1 yarn e2e path/to/file.e2e.ts
+```
+
+### Project-wide (use sparingly)
+
+```bash
+# Development
+yarn dev              # Start dev server
+yarn dx               # Dev with database setup
+
+# Build & check
+yarn build            # Build all packages
+yarn lint:fix         # Lint and fix all
+yarn type-check       # Type check all
+
+# Tests (use TZ=UTC for consistency)
+TZ=UTC yarn test      # All unit tests
+yarn e2e              # All E2E tests
+
+# Database
+yarn prisma generate  # Regenerate types after schema changes
+yarn workspace @calcom/prisma db-migrate  # Run migrations
+```
+
+## Boundaries
+
+### Always do
+- Run type check on changed files before committing
+- Run relevant tests before pushing
+- Use `select` in Prisma queries
+- Follow conventional commits for PR titles
+
+### Ask first
+- Adding new dependencies
+- Schema changes to `packages/prisma/schema.prisma`
+- Changes affecting multiple packages
+- Deleting files
+- Running full build or E2E suites
+
+### Never do
+- Commit secrets, API keys, or `.env` files
+- Expose `credential.key` in any query
+- Use `as any` type casting
+- Force push or rebase shared branches
+- Modify generated files directly
+
+## Project Structure
+
+```
+apps/web/                    # Main Next.js application
+packages/prisma/             # Database schema (schema.prisma) and migrations
+packages/trpc/               # tRPC API layer (routers in server/routers/)
+packages/ui/                 # Shared UI components
+packages/features/           # Feature-specific code
+packages/app-store/          # Third-party integrations
+packages/lib/                # Shared utilities
+```
+
+### Key files
+- Routes: `apps/web/app/` (App Router)
+- Database schema: `packages/prisma/schema.prisma`
+- tRPC routers: `packages/trpc/server/routers/`
+- Translations: `apps/web/public/static/locales/en/common.json`
+- Workflow constants: `packages/features/ee/workflows/lib/constants.ts`
+
+## Tech Stack
+
+- **Framework**: Next.js 13+ (App Router in some areas)
+- **Language**: TypeScript (strict)
+- **Database**: PostgreSQL with Prisma ORM
+- **API**: tRPC for type-safe APIs
+- **Auth**: NextAuth.js
+- **Styling**: Tailwind CSS
+- **Testing**: Vitest (unit), Playwright (E2E)
+- **i18n**: next-i18next
+
+## Code Examples
+
+### Good error handling
+
+```typescript
+// Good - Descriptive error with context
+throw new TRPCError({
+  code: "BAD_REQUEST",
+  message: `Unable to create booking: User ${userId} has no available time slots for ${date}`,
+});
+
+// Bad - Generic error
+throw new Error("Booking failed");
+```
+
+### Good Prisma query
+
+```typescript
+// Good - Use select for performance and security
+const booking = await prisma.booking.findFirst({
+  select: {
+    id: true,
+    title: true,
+    user: {
+      select: {
+        id: true,
+        name: true,
+        email: true,
+      }
+    }
+  }
+});
+
+// Bad - Include fetches all fields including sensitive ones
+const booking = await prisma.booking.findFirst({
+  include: { user: true }
+});
+```
+
+### Good imports
+
+```typescript
+// Good - Type imports and direct paths
+import type { User } from "@prisma/client";
+import { Button } from "@calcom/ui/components/button";
+
+// Bad - Regular import for types, barrel imports
+import { User } from "@prisma/client";
+import { Button } from "@calcom/ui";
+```
+
+## PR Checklist
+
+- [ ] Title follows conventional commits: `feat(scope): description`
+- [ ] Type check passes: `yarn type-check:ci --force`
+- [ ] Lint passes: `yarn lint:fix`
+- [ ] Relevant tests pass
+- [ ] Diff is small and focused (<500 lines, <10 files)
+- [ ] No secrets or API keys committed
+- [ ] UI strings added to translation files
+- [ ] Created as draft PR
+
+## When Stuck
+
+- Ask a clarifying question before making large speculative changes
+- Propose a short plan for complex tasks
+- Open a draft PR with notes if unsure about approach
+- Fix type errors before test failures - they're often the root cause
+- Run `yarn prisma generate` if you see missing enum/type errors
+
+## Extended Documentation
+
+For detailed information, see the `agents/` directory:
+
+- **[agents/README.md](agents/README.md)** - Architecture overview and patterns
+- **[agents/commands.md](agents/commands.md)** - Complete command reference
+- **[agents/knowledge-base.md](agents/knowledge-base.md)** - Domain knowledge and best practices
+- **[agents/coding-standards.md](agents/coding-standards.md)** - Coding standards with examples