Feature: Prompt for SSH key passphrase during commit/push/PR #3813

Summary

When using an SSH key protected by a passphrase, git operations (push/pull) require entering the SSH key password. In VS Code, this surfaces as a top-of-window popup that asks for the SSH key passphrase. T3 Code currently errors out instead of prompting.

Problem

If you use a passphrase-protected SSH key, running one-click commit, push, and create PR in T3 Code fails because there is no way to supply the SSH passphrase. The operation should not hard-fail; it should interactively collect the credential and continue.

Proposed solution

When git/SSH needs a passphrase (e.g. during push as part of commit + push + open PR):

1. Show a popup/modal asking for the SSH key passphrase (similar to VS Code).
2. Pass the passphrase into the git/SSH pipeline for that operation.
3. Complete the full flow (commit → push → create PR) without requiring the user to leave T3 Code.

Img from vscode's popup:

Motivation

• Matches the familiar VS Code UX for passphrase-protected SSH keys.
• Makes one-click commit/push/PR usable for users who secure their keys with a passphrase.
• Avoids opaque failures when SSH agent doesn’t already hold the unlocked key.

Acceptance criteria

• Passphrase-protected SSH keys prompt the user instead of failing the push.
• Entered passphrase is used only for the active git/SSH operation (not persisted insecurely).
• One-click commit + push + create PR completes successfully after the user provides the passphrase.
• Behavior is consistent with other credential prompts in the product where applicable.

Additional context

Works fine when the key is already unlocked (e.g. via ssh-agent). The gap is interactive prompting when the key is locked, especially during automated multi-step git flows.

Error message

Git command failed in GitVcsDriver.pushCurrentBranch.pushWithUpstream (/Users/username/personal/projects): Git command exited with a non-zero status.