docs(claude): add path-scoped frontmatter to four agent rules (#29612)

Adds `paths:` YAML frontmatter so each rule only loads into Claude Code
context when the agent is working on relevant files, keeping context lean
in a large monorepo.

- architecture-page-level-auth: fires on page.tsx and layout.tsx
- data-prisma-migrations: fires on packages/prisma/**
- testing-playwright: fires on playwright dirs, *.e2e.ts, and api e2e dirs
- api-thin-controllers: fires on *.controller.ts files only

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

agents/rules/api-thin-controllers.md

@@ -1,4 +1,6 @@
 ---
+paths:
+  - "apps/api/**/*.controller.ts"
 title: Keep Controllers Thin - HTTP Concerns Only
 impact: HIGH
 impactDescription: Enables technology-agnostic business logic

agents/rules/architecture-page-level-auth.md

@@ -1,4 +1,7 @@
 ---
+paths:
+  - "apps/**/page.tsx"
+  - "apps/**/layout.tsx"
 title: Page-Level Authorization Checks in Next.js
 impact: CRITICAL
 impactDescription: Prevents unauthorized access to sensitive data

agents/rules/data-prisma-migrations.md

@@ -1,4 +1,6 @@
 ---
+paths:
+  - "packages/prisma/**"
 title: Prisma Schema and Migrations
 impact: HIGH
 impactDescription: Schema changes affect all downstream code and deployments

agents/rules/testing-playwright.md

@@ -1,4 +1,9 @@
 ---
+paths:
+  - "apps/web/playwright/**"
+  - "packages/embeds/**/playwright/**"
+  - "apps/**/*.e2e.ts"
+  - "apps/api/**/e2e/**"
 title: Playwright E2E Testing
 impact: HIGH
 impactDescription: E2E tests catch integration issues before production