[FEATURE] Option to set output style in non-interactive mode

Description

Currently (v1.0.81) output styles as introduced in the recent release only work in interactive mode via /output-style command. There's no way to use custom output styles with the -p (print/headless) mode, which limits automation and scripting capabilities.

## Current Behavior

• Output styles can only be set interactively using /output-style [style]
• The outputStyle field in .claude/settings.local.json doesn't affect -p

mode

• Custom output styles in .claude/output-styles/ cannot be used with headless

execution

## Desired Behavior

Add support for output styles in non-interactive mode through one or more of
these approaches:

1. CLI flag: claude -p "prompt" --output-style french-teacher
2. Settings respect: Have -p mode respect the outputStyle field in

settings.json

1. System prompt integration: Allow output style files to be loaded as system

prompts

## Use Cases

• Automated generation with specific communication styles (e.g., different

languages, educational modes)

• Batch processing with custom output requirements
• Integration with tools expecting specific output formats