[Bug]: "Add" enhancement modes replace description instead of adding to it

[Ridimo]

Operating System

Windows

Run Mode

Docker

App Version

0.13.0

Bug Description

When using the "Enhance with AI" feature on a feature description, the modes that are supposed to add content to the existing description instead replace it entirely.

Modes that should replace (working correctly):

• Improve Clarity - rewrites the description (correct)
• Simplify - rewrites the description (correct)

Modes that should be additive (broken):

• Add Technical Details - replaces the description instead of adding technical details below it
• Add Acceptance Criteria - replaces the description instead of adding acceptance criteria below it
• User Experience - replaces the description instead of adding UX considerations below it

Steps to Reproduce

1. Create or edit a feature with a description (e.g., "Add a login page with email and password fields")
2. Open "Enhance with AI"
3. Select "Add Acceptance Criteria" and click Enhance
4. The original description is gone, replaced entirely by the AI output

Expected Behavior

The original description should be preserved, with the new content (acceptance criteria, technical details, UX considerations) appended below it.

Actual Behavior

The original description is completely overwritten by the AI-generated text.

Screenshots

No response

Relevant Logs

Additional Context

my current version is 0.13.0 but it should be 0.14.0 because the v0.14.0rc is actually merged on main

Checklist

• I have searched existing issues to ensure this bug hasn't been reported already
• I have provided all required information above

[gsxdsm]