Enforce strict multi-line Markdown format for AI-generated issue descriptions

[thomas-vilte]

Description

I have updated the AI's issue content generation to strictly enforce multi-line Markdown formatting for the description field. This change modifies the Gemini schema and the internal prompts to explicitly instruct the AI to generate descriptions with real line breaks between headers, paragraphs, and list items, rather than using \n escape sequences or collapsing sections into a single line.

This ensures that AI-generated issue descriptions are naturally formatted, readable Markdown documents, mirroring how a person would type them in a text editor.

Fixes #

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce.

• Unit tests
• Integration tests
• Manual test: (describe below)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Test Plan & Evidence

Suggested Manual Verification

• Unit Tests: Run go test ./... and ensure all tests pass
• No Regressions: Verify that related features still work as expected