Support migrated GitLab work items in issue:branch and bare NID resolution

[mglaman]

Fixes #380.

issue:branch failed for an issue that migrated from Drupal.org to a GitLab work item, in every form the reporter tried: bare NID, project#nid, and the work item URL. The error said the node was not found, which was wrong.

What changed

• Migrated nodes are recognized. Drupal.org answers a migrated NID with a stub whose only field is new_url. Client::getNode() now throws MigratedIssueException carrying the parsed work item ref. The message names the qualified ref to pass. Commands without work item support show that instead of "not found".
• Bare NIDs resolve. IssueProjectResolver takes the project from that ref, so issue:get-fork 3617735, issue:setup-remote 3617735, and issue:checkout 3617735 work with no qualifier and no extra request.
• issue:branch supports work items. The action takes the ref, or follows a migrated node to GitLab. The branch slug comes from the work item title. The base branch comes from the version label (v2.0.x-dev gives 2.0.x) and falls back to the project's default branch when there is no version label, which is the case on ai_context.
• issue:show follows the migration. A bare NID for a migrated issue renders the work item instead of stopping with the migration error.
• Wrong-repository message names the work item. When the redirect points at project A and you are in a clone of project B, the resolver says the work item lives in A instead of offering a Drupal.org issue that no longer exists.
• IssueCommandBase opens the repository for work item refs. It returned early after parsing project#nid or a URL, so any command that used the repository crashed with an uninitialized property.
• The slug and version-branch rules move from IssueNode to IssueBranchNaming so both sources name branches the same way. That commit is a pure refactor.

Testing

Unit tests cover the migrated stub in getNode(), the resolver with and without a repository project, the collision case, work items with and without a version label, and a bare NID that follows the redirect to GitLab.

Live, in a clone of restrict_route_by_ip, without a token:

drupalorg issue:branch 3617735
drupalorg issue:branch restrict_route_by_ip#3617735
drupalorg issue:branch https://git.drupalcode.org/project/restrict_route_by_ip/-/work_items/3617735

Each checks out 2.0.x and creates 3617735-fix_js_on_add_form_a. issue:show 3617735, issue:get-fork 3617735, and issue:checkout 3617735 also work with the bare NID. issue:setup-remote 3617735 from a clone of poll prints the work item collision message and adds no remote.

🤖 Generated with Claude Code