feat: add render_prompt function for --format prompt output

[krishkhatik01]

PR Summary: Add --format prompt Output Support

Overview
Introduced a new render_prompt function to support the --format prompt CLI option. This allows users to output the raw, unformatted prompt directly to the terminal, bypassing the standard Markdown or HTML wrapping.

Key Changes

• render.py: Added the render_prompt(pack) function, a clean, two-line utility that extracts and returns pack.prompt directly.
• cli.py:
  • Imported the new render_prompt function.
  • Added "prompt" as a valid option to the --format argument parser choices.
  • Updated main() to handle the choice and trigger render_prompt(pack) accordingly.
• test_issue_to_agent.py:
  • Updated existing renderer test coverage to include the new prompt renderer.
  • Added an end-to-end integration test (test_cli_writes_prompt_only_output) to ensure the CLI cleanly handles the new flag.

Testing & Status

• All 12 unit and integration tests are passing successfully.
• The branch is currently rebased, clear of conflicts, and ready for review.

[itscloud0]

Thanks for the contribution. I verified the feature locally, cleaned up whitespace, documented the new format, and CI is green.