[FEATURE] Setting to disable plan file creation

Use Case

Teams using enterprise task/planning management systems (Jira, Azure DevOps, internal tools) don't need Claude Code's local plan files. These files:

1. Have random names (e.g., purrfect-weaving-globe.md) with no relation to actual task identifiers
2. Are local-only - can't be shared across team members or synced with enterprise systems
3. Conflict with existing workflows - teams may already have plan templates, approval processes, and tracking in their task management system
4. Create clutter - accumulate in ~/.claude/plans/ with no automatic cleanup

Current Behavior

• Plan mode always creates files in ~/.claude/plans/ (or plansDirectory in v2.1.9+)
• No way to disable file creation entirely
• plansDirectory only redirects, doesn't disable

Requested Feature

Add a setting to completely disable plan file creation:

Option 1: Settings.json

{
  "planFilesEnabled": false
}

Option 2: Environment Variable

export CLAUDE_CODE_DISABLE_PLAN_FILES=1

Expected Behavior

When disabled:

• Plan mode still works (read-only exploration, design discussions)
• Claude's plan content shown in terminal output
• No files written to disk
• Users can copy plan content to their own task system if needed

Workaround Attempted

Setting ~/.claude/plans to read-only - behavior unknown, may cause errors.

Environment

• Platform: Linux (WSL2)
• Using internal task management system for all planning
• Multiple developers on team