Exclude .claude/worktrees from ESLint to clean lint output

Problem

pnpm lint currently reports 20 ESLint errors — every one of them comes from generated files in .claude/worktrees/<branch>/.next/ directories created by Claude Code's worktree feature. None of them are real source files; they are throwaway build artifacts in temporary worktrees that get cleaned up automatically. The noise hides any real lint regressions.

Evidence

• pnpm lint 2>&1 | head -30 shows errors only under .claude/worktrees/.../.next/.
• pnpm exec eslint src --max-warnings 0 is clean — confirming the issue is purely the worktree artifacts.

Proposed approach

1. Open eslint.config.mjs (flat config — top-level ignores array).
2. Add .claude/worktrees/** (and **/.next/** for safety) to the global ignores:

   {
     ignores: [
       \".claude/worktrees/**\",
       \"**/.next/**\",
       \"node_modules/**\",
       \"dist/**\",
       // ...existing ignores
     ],
   },
   

3. Confirm pnpm lint returns zero errors after the change.
4. Update .gitignore if .claude/worktrees is not already covered (it should be, but verify).

Acceptance criteria

• pnpm lint exits 0 with no errors and no warnings.
• pnpm exec eslint src --max-warnings 0 continues to be clean.
• .claude/worktrees/ directory is git-ignored (confirm with git check-ignore).
• pnpm typecheck still passes.

Verification

1. pnpm lint → exit 0, zero errors.
2. Create an obvious lint error in src/lib/utils.ts (e.g. unused variable) → pnpm lint reports it. Revert.
3. Re-run pnpm lint → clean again.

Start with eslint.config.mjs and inspect the existing top-level ignores, then verify .claude/worktrees/ coverage in .gitignore with git check-ignore. Run pnpm lint, pnpm exec eslint src --max-warnings 0, and pnpm typecheck before and after the configuration change. Done means lint exits cleanly, the existing src check and typecheck still pass, and a temporary lint error in src/lib/utils.ts is detected.