Add support for configuring a dedicated SSH key file per author

[hnrobert]

Summary

Add support for configuring a dedicated SSH key file per author, so that when switching authors via git-mob, the corresponding SSH identity can also be switched automatically for Git operations (e.g., push).

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Motivation

Currently, git-mob focuses on managing co-author metadata (name/email), but in multi-account environments (e.g., personal + work GitHub accounts on GitHub), author identity is often tightly coupled with SSH credentials.

A common workflow issue:

• Different authors correspond to different GitHub accounts
• Each account requires a distinct SSH key
• Git itself selects SSH keys independently of git config user identity
• As a result, switching author via git-mob does not ensure the correct authentication identity is used during git push

This leads to frequent errors such as:

• Write access to repository not granted
• Authentication as the wrong user

Desired behavior

When switching author via git-mob:

• The corresponding SSH key should also be selected automatically
• Git operations (especially push) should use the correct identity without manual overrides

Example use case

• Selecting alice as the main author -> automatically uses ~/.ssh/id_ed25519_alice
• Selecting bob as the main author -> automatically uses ~/.ssh/id_ed25519_bob

This would align author identity (commit metadata) with authentication identity (SSH key), reducing friction in multi-account workflows.

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Describe alternatives you've considered

1. Manual SSH command override

GIT_SSH_COMMAND="ssh -i ~/.ssh/key" git push

• Works, but not scalable
• Requires manual intervention every push

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2. Git config per-repo

git config core.sshCommand "ssh -i ~/.ssh/key"

• Static, not compatible with dynamic author switching

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3. SSH config with multiple hosts

Host github-work
  IdentityFile ~/.ssh/work_key

Host github-personal
  IdentityFile ~/.ssh/personal_key

• Requires changing remote URLs
• Breaks abstraction git-mob provides
• Not author-driven

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4. Wrapper scripts / aliases

• Adds complexity outside the extension
• Hard to maintain and onboard for teams

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Proposed approach

Extend git-mob configuration to support SSH key mapping, similar to (not necessarily the final version, just for ref)

{
  "gitMob.authorSSHKeys": {
    "alice": "~/.ssh/id_ed25519_alice",
    "bob": "~/.ssh/id_ed25519_bob"
  }
}

When switching author, we can do things similar to:

• Update core.sshCommand dynamically, or
• Inject GIT_SSH_COMMAND for Git operations triggered via the extension

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Additional context

This would be a relatively large change, as it crosses from identity management into Git transport configuration.

If this is considered out of scope for the project, I am happy to explore this as a separate fork or extension.

However, given how common multi-account setups are, this feature could significantly improve usability for teams working across multiple Git identities.

[hnrobert]

I am assignable to this issue, and you can optionally allow me to work on this, in a way easier for you to merge.

If a pr doing this is unfortunately not welcomed... I'm also prepared to rewrite the whole project in my preferred way (pnpm + ts + tsup, or something like that...), because this feature is needed for me, personally, and I would try my best to achieve this ;)