Inherit default pull request descriptions from bitbucket repo

**Is your feature request related to a problem? Please describe.**

When creating a pull request in Bitbucket Web, the Description field is populated using the repository's configured **Default pull request description**.

When creating the same pull request through Atlassian for VS Code, the Description field remains empty. The extension does not appear to inherit or apply the repository-level setting.

**Describe the solution you'd like**

The Atlassian for VS Code Create Pull Request form should inherit and apply the selected repository's **Default pull request description**.

It should:

- Retrieve the default description configured for the destination repository.
- Display the configured text in the PR Description field when creating a PR

The goal is for the initial PR form in VS Code to match the initial PR form in Bitbucket Web.

**Describe alternatives you've considered**

Current workarounds include:

Either creating the pull request through the bitbucket webapp
or
copy the generated the commit list manually with:
`git log --reverse --pretty=format:'- %s' origin/main..HEAD`

and paste it into the description field

Start by locating the Create Pull Request form and tracing how it loads settings for the selected Bitbucket destination repository. Check the existing tests around pull request creation or repository settings before making changes. Done means the configured default description appears in the form and the behavior is covered by a test.

Written by the indexing model from the issue text.