workflow-extend

Announce at start: "Using swe-workbench:workflow-extend — capturing and implementing sub-idea onto the existing PR."

When to invoke

• /swe-workbench:extend command
• "extend the PR", "add this on top of the current PR"
• Mid-PR follow-on idea surfaces while working on an in-flight branch
• Related sub-idea that belongs on the same branch and same PR

When NOT to invoke

• No open PR exists for the current branch → command body owns the fallback (AskUserQuestion)
• Sub-idea is unrelated to current PR → use /swe-workbench:implement for a fresh branch
• PR is already merged → use /swe-workbench:implement for a follow-up PR
• Bug on someone else's PR → use /swe-workbench:debug

Precondition