fix(tsconfig): set rootDir explicitly in feature packages

TypeScript emits an informational diagnostic when source files span
multiple top-level dirs (src/ + tests/) without explicit rootDir.
Setting rootDir="." satisfies the recommendation and matches the
include pattern. Updates blog, auth, marketing-pages — and Plan 4
doc so navigation (still pending) starts correct.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/superpowers/plans/2026-05-04-plan-4-marketing-pages-navigation.md

@@ -152,6 +152,7 @@
   "extends": "@repo/typescript-config/base.json",
   "compilerOptions": {
     "outDir": "dist",
+    "rootDir": ".",
     "lib": ["ES2022", "DOM"],
     "jsx": "preserve",
     "paths": {