linear support

[zebapy]

We use linear instead of github issues. Would love to see that supported. This is nearly the kind of workflow UI I've dabbled with making a few times. Nice work!

[michael-dg]

+1 — my whole workflow runs on Linear (specs → leaf issues → one worktree per issue), so this is the main thing keeping me from switching to nebula full-time. I'd be glad to help build it. To keep the core lean, would you be open to an "issue source" abstraction, configured the way harnesses are in config.json — GitHub stays the default, Linear becomes one more source? Happy to sketch the shape before writing any code.