[FEATURE] Support non-origin remotes

[jchauncey]

Problem

[IsolationManager] Created worktree isolation at /var/folders/g5/2pf97_f57cn_4swz9yrzhblw0000gn/T/zeroshot-worktrees/gleaming-tiger-67
[IsolationManager] Branch: zeroshot/gleaming-tiger-67
Cluster gleaming-tiger-67 failed to start: Error: --pr mode failed: Cannot determine git platform for --pr mode. Ensure you are in a git repository with a remote URL from GitHub, GitLab, or Azure DevOps.
    at Orchestrator._applyAutoPrConfig (/Users/chauncey/.nvm/versions/node/v23.10.0/lib/node_modules/@covibes/zeroshot/src/orchestrator.js:1240:13)
    at Orchestrator._startInternal (/Users/chauncey/.nvm/versions/node/v23.10.0/lib/node_modules/@covibes/zeroshot/src/orchestrator.js:775:12)
    at async Command.<anonymous> (/Users/chauncey/.nvm/versions/node/v23.10.0/lib/node_modules/@covibes/zeroshot/cli/index.js:2483:23)
Error: --pr mode failed: Cannot determine git platform for --pr mode. Ensure you are in a git repository with a remote URL from GitHub, GitLab, or Azure DevOps.

This is from running zeroshot run <issue> --pr where I don't user origin as the default remote. I use upstream for the non-fork version of my repos and it seems like its trying to find the remote by an explicit look up of origin.

What problem does this solve?
Allows more flexibility of a users git repo

Proposed Solution

Either allow the remote name to be passed in as a flag or set in configuration.

How should it work?

Alternatives Considered

What other options did you consider?

Additional Context

Any other relevant information.