Diagnostics reporter flags Deno files with false TypeScript errors (doesn't respect tsconfig exclude)

Summary

Claude Code's built-in diagnostic reporter surfaces TypeScript errors for Deno files (.ts files under scripts/pipeline/) even though these paths are explicitly excluded in the project's root tsconfig.json. The diagnostics are false positives — the files type-check correctly under Deno's own type checker.

Reproduction

1. Have a monorepo with a root tsconfig.json that excludes a directory:

``json
{
"exclude": ["node_modules", "supabase/functions", "scripts/pipeline"]
}
``

1. That excluded directory contains Deno TypeScript files using Deno.* APIs and @std/* imports
2. Open a Claude Code session in the repo root
3. Edit or view any Deno file — diagnostics appear:

``
✘ [Line 79:1] Cannot find name 'Deno'. [2304] (typescript)
✘ [Line 8:30] Cannot find module '@std/assert'. [2307] (typescript)
``

These appear as <system-reminder><new-diagnostics> messages in the conversation, adding noise on every tool use.

Expected behavior

The diagnostic reporter should respect tsconfig.json exclude paths. Files in excluded directories should not be type-checked by the TypeScript language service.

Alternatively, provide a Claude Code setting to exclude paths from diagnostics:

{
  "diagnostics": {
    "exclude": ["scripts/pipeline/**"]
  }
}

Environment

• Claude Code CLI v2.1.84
• Monorepo with Expo/React Native (Node TypeScript) + Deno pipeline scripts
• Root tsconfig.json excludes scripts/pipeline
• Deno files have their own deno.json config

Impact

Low — purely cosmetic. Diagnostics don't affect tool execution, tests, or CI. But they add significant noise to conversations, especially when editing multiple files in succession.