Flatten the nested next/ app directory up to the repository root, removing
the `cd next` friction that the old .cursor/rules existed largely to manage.

- Move all app files (pages, components, lib, styles, content, public,
  tests, scripts, configs) and Yarn Zero-Install state (.pnp.cjs, .yarn/)
  from next/ to repo root via git mv (history preserved, 316 renames).
- Merge next/.gitignore into the root .gitignore; note .pnp.cjs/.yarn are
  committed (Zero-Install) and must not be ignored.
- Pin outputFileTracingRoot to the project in next.config.js: a stray
  ~/package-lock.json was making Next infer the wrong workspace root.
  Also makes standalone output tracing correct for self-hosting later.
- Update CLAUDE.md: commands run from repo root; @/ alias, content/,
  public/, .next/ paths corrected; Vercel root dir must become '.'.

Build green from root (yarn build, Node 20, all 14 route patterns, zero
warnings). Content loaders (process.cwd()-based) resolve correctly since
content/ and public/ now sit at the root.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>