Add glab-backed GitLab issue polling, login lookup, and comment posting so GitLab projects can be handled alongside GitHub, Gitea, and OpenProject. Also wire GitLab through SCM selection, config defaults, docs, and examples so issue #35 can be configured end to end.
* feat: add github webhook-forward event source for #12
Add a channel-based GitHub issue source so long-running sessions can react to issue and issue_comment webhooks without polling. Keep --once on polling so backlog reconciliation still works and cover the new config/runtime path with tests.