fix: render branch creation dialog in TaskInput screen

[CaioDGallo]

Problem

• when clicking to "Create a new branch" on the BranchSelector component of the TaskInput page, nothing happens because the GitBranchDialog is never rendered in this flow.

Closes #1205

Changes

• Added GitBranchDialog component to the TaskInput screen
• Handled branch name sanitization and branch creation logic for this step (integrated with useGitInteractionStore props)
• Added branch-here to GitActionType to fix linter issue
• Extracted branch sanitize/validate/create flow into shared branchCreation utility used by both TaskInput and useGitInteraction (no intended behavior change).

How did you test this?

Manually

[CaioDGallo]

Hi @charlesvien , I submitted this PR to fix #1205. The "Create new branch" dialog wasn't rendering on the TaskInput screen because GitInteractionHeader (which hosts the dialog) is only mounted in the task detail view. The fix adds the dialog rendering directly in TaskInput, driven by the existing gitInteractionStore.

Happy to hear your thoughts when you have time. Thanks!