feat: Implement true non-interactive mode for -p/--prompt flag

[liciciyi]

Summary

This PR implements a true non-interactive mode for the -p/--prompt flag, similar to Claude Code's --print mode. Instead of rendering the TUI interface, the CLI now outputs pure text responses and exits automatically.

Changes

Core Implementation (packages/cli/src/cli.tsx)

• Added runNonInteractiveMode() function that bypasses Ink/React UI entirely
• Uses SessionManager directly to process prompts
• Outputs only the LLM response as plain text to stdout
• Handles errors gracefully with stderr output and proper exit codes
• Imports necessary types and functions from @vegamo/deepcode-core

Behavior

Before:

$ deepcode -p "hello"
[Shows full TUI with banner, status bar, etc.]
[User must manually exit]

After:

$ deepcode -p "hello"
Hello! I'm Deep Code, an interactive CLI tool designed to help you with software engineering tasks.
...
[Auto-exits with code 0]

Testing & Verification

All Tests Pass ✅

• Core package: 255/255 tests passed
• CLI package: 253/254 tests passed (1 skipped)
• UI package: 49/49 tests passed
• Total: 557/558 tests passed

Build Verification ✅

• TypeScript type checking: Passed
• ESLint: Passed
• Prettier formatting: Passed
• Full build: Successful

Functional Testing ✅

• Non-interactive mode works correctly
• Pure text output without ANSI escape codes
• Auto-exit after response confirmed
• Exit code 0 on success verified
• Error handling tested

Use Cases

This feature enables:

• Scripting and automation workflows
• Integration with other CLI tools
• Quick queries without entering interactive mode
• CI/CD pipeline integration

Related Issues

Fixes Issue #252: Make -p flag exit after response

Checklist

• Code follows project style guidelines
• Self-review completed
• Tests added/updated and passing
• Documentation updated (help text reflects new behavior)
• No breaking changes to existing functionality