Decouple Prettier from ESLint

[gonzaloriestra]

Why

This is the first step of the ESLint-to-Oxlint migration. It separates formatting from linting so later PRs can change the linter without changing formatting behavior.

What changed

• add standalone prettier and prettier:fix scripts for the source files currently linted
• run formatting explicitly in local lint scripts and GitHub Actions
• format GraphQL codegen output directly with Prettier
• remove the prettier/prettier ESLint rule while retaining compatibility rules that prevent formatter conflicts
• move Prettier to the workspace root and remove the direct eslint-plugin-prettier dependency
• document the standalone formatting commands

Validation

• pnpm install --frozen-lockfile
• pnpm prettier
• pnpm nx run-many --all --skip-nx-cache --target=lint --output-style=stream
• verified eslint --print-config does not contain prettier/prettier

[gonzaloriestra]

• Remove the ESLint compatibility layer #8211
• Close remaining Oxlint parity gaps #8210
• Run local CLI rules with Oxlint #8209
• Make Oxlint the primary linter #8208
• Add type-aware Oxlint alongside ESLint #8206
• Decouple Prettier from ESLint #8204 👈 (View in Graphite)
• main

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