/co:build

Execute the next pending task in the current change.

Preconditions

• There must be an active change. If the user hasn't run /co:change yet, refuse and redirect them.
• Determine the active change: read openspec/changes/*/CHANGE.md; the one whose backing task-thread is newest + not archived is active. If multiple, ask which.

Procedure

1. Find the next task

Read CHANGE.md §T. The next task is the first row with status . (todo). If all are x (done) or ~ (wip-by-someone-else), stop — nothing to build.

2. Claim it

Call task_claim_file with file_path = "CHANGE.md#T<n>" so other agents on this spec thread see the claim. Overlapping claims surface in attention_inbox on their next turn.