[itdove]

Description

#651: bug: GitLab source-branch picker silently falls back to text input

Changes in this branch:

• fix: explain source branch discovery fallback

Related issue (if applicable)

Closes #651 (issue)

Type of change

• Bug fix
• New feature
• Security fix or detection change
• Documentation or workflow change
• Refactoring or maintenance

Security impact

• This change has no security impact.
• This change affects security behavior; describe the threat, protection, and user-visible behavior below.

Security behavior is implicated by the session context; review the threat and user-visible impact before merging.

Testing

• Tests added or updated where needed.
• Related tests pass locally. (test results not captured in session context)
• Manual verification completed, if applicable. (manual verification not captured in session context)

Evidence from session context:

• Test files changed: tests/test_git_utils.py, tests/test_source_branch_selection.py
• Test command results were not captured in the session metadata.

Commands run

No command evidence was captured in the session context.

Checklist

• The change is limited to this PR's purpose.
• Documentation is updated where needed.
• CHANGELOG.md is updated for notable changes, or no update is needed.
• Backward compatibility was considered for the public SDK and configuration. (not independently verified in session context)
• New dependencies have compatible licenses, if applicable. (no new dependencies identified)
• UX contract tests are included when user-visible security behavior changes.