[Feature Request] Add --plan-file and --plan-only flags for non-interactive planning mode

Bug Description
Feature Request: Non-Interactive Planning Mode Enhancements

Problem Statement

When running Claude Code in planning mode (--permission-mode plan) with the -p flag for non-interactive/headless execution, the CLI still prompts for user approval before proceeding. This blocks automation workflows and background job usage.

Additionally, plan files are written to ~/.claude/plan/<random-name>.md with no way to specify a custom location, making it difficult to programmatically retrieve the generated plan.

Proposed Solution

Add the following CLI flags:

| Flag | Description |
|--------------------|-------------------------------------------------------|
| --plan-file <path> | Specify custom output path for the plan file |
| --plan-only | Generate plan and exit without prompting for approval |

Example Usage

# Generate plan to specific file and exit
claude --permission-mode plan \
-p "Create migration plan for OAuth" \
--plan-file ./plans/oauth-migration.md \
--plan-only

# Use in CI/scripts
claude --permission-mode plan \
-p "$(cat requirements.md)" \
--plan-file /tmp/plan.md \
--plan-only && cat /tmp/plan.md

Use Cases

1. Background jobs - Generate plans overnight for review next morning
2. CI pipelines - Auto-generate implementation plans from issue descriptions
3. Batch processing - Queue multiple planning requests
4. Documentation - Automatically save plans to project directories
5. Review workflows - Generate plans for team review before execution

Current Workarounds

• Watching ~/.claude/plan/ for new files (brittle, race conditions)
• Using --max-turns to limit execution (doesn't guarantee clean exit)
• Symlinking the plan directory (doesn't solve the approval prompt)

Additional Context

The -p flag successfully enables non-interactive mode for normal operations, so extending this to planning mode would be consistent with existing CLI behavior.

Environment Info

• Platform: darwin
• Terminal: tmux
• Version: 2.0.76
• Feedback ID: 4f337205-7261-400a-b442-5bb9158e479f

Errors

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