Feature — create a feature branch + crosslink issue

The user will provide a human-readable description of the feature (e.g. "add batch retry logic"). Create a feature branch following the project's naming convention.

1. Derive the branch name

• Slugify the description: lowercase, strip non-alphanumeric characters (except hyphens), replace spaces with hyphens, collapse consecutive hyphens.
• The branch name is feat/<slug> (e.g. feat/add-batch-retry-logic), matching the repo convention (e.g. feat/stealth-js-instrument-v2).
• If the slug is empty or the branch already exists, ask the user for a different name.

2. Validate preconditions

• Confirm there are no unexpected working-copy changes (jj status). In jj the working copy is always a commit, so changes don't block branching — but warn the user if the diff is unexpectedly large and ask whether to proceed.
• Identify the base revision. Default to @ (the current change). If the user provides a --from <ref> argument, use that instead.

3. Create the bookmark

jj bookmark create feat/<slug> -r <base-ref>
jj new feat/<slug> -m "wip: start feat/<slug>"

This creates the feat/<slug> bookmark and starts a new change on top of it. Always pass -m to jj new. Print the created bookmark name so the user can confirm.

4. Track in crosslink

• Create a crosslink issue for the feature work with the user's original description as the title.
• Set priority to medium (unless the user specifies otherwise).
• Use: crosslink issue create "<description>" -p medium --label feature

Constraints

• Never force-push or delete bookmarks.
• Do not push the bookmark to a remote — the user will do that when ready.
• Keep the slug concise. If the description is very long, truncate to the first 6-8 meaningful words.
• Always pass -m to jj commands — never let jj open an editor.