feat: simplify ESLint config - Prettier for formatting, ESLint for correctness

[pyramation]

Summary

Simplifies the linting setup to follow the recommended pattern: Prettier handles all formatting, ESLint handles only correctness and import sorting.

ESLint changes:

• Removed all formatting rules (indent, quotes, semi, comma-dangle, etc.) - Prettier handles these
• Removed unused-imports plugin
• Removed TypeScript rule overrides - using recommended defaults
• Removed env block
• Changed import-sort rules from warnings to errors

Prettier changes:

• trailingComma: "es5" → "all"
• Added explicit printWidth: 80
• Removed redundant defaults (tabWidth, useTabs, jsxSingleQuote)

Review & Testing Checklist for Human

• Verify env removal is safe: The removal of env: { node: true, jest: true, browser: true } may cause no-undef errors for globals like process, describe, it. Run pnpm lint on a few packages to confirm no false positives
• Confirm TypeScript defaults are acceptable: Removing overrides means @typescript-eslint/no-explicit-any becomes a warning and @typescript-eslint/no-unused-vars uses default patterns - verify this is desired
• Test trailingComma: "all" impact: This will add trailing commas to function parameters when Prettier runs - confirm this style is acceptable

Test plan: Run npx eslint packages/cli/src/index.ts to verify ESLint works without errors on the config itself.

Notes

This PR contains config changes only. A follow-up PR will apply the actual linting fixes to the codebase.

Link to Devin run: https://app.devin.ai/sessions/1a95a9e3b5994325aeffe5ae1289aa0a
Requested by: Dan Lynch ([email protected]) / @pyramation

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