Per RFC §15.5.1: agent branches (agent/*) must be deleted from Forge
after successful push or merge — stale branches pollute workspace prep
and cause clone confusion.
Lands:
* pkg/agentic/branch_cleanup.go (NEW) — cleanupBranch(ctx, repo, branch)
helper. Refuses main/dev/master regardless of input (defensive).
Normalises refs/heads/* prefix. Treats missing-remote-branch as
harmless cleanup-success (idempotent).
* pkg/agentic/branch_cleanup_test.go (NEW) — AX-10 TestCleanupBranch_
{Good_DeletesAgentBranch, Bad_RefuseProtected, Ugly_DeleteFailsForge}.
* pkg/agentic/pr.go — createPR success-on-push path now calls cleanupBranch.
* pkg/agentic/commands.go — cmdComplete success path also calls cleanupBranch.
* tests/cli/branch/Taskfile.yaml — end-to-end smoke + AX-10 unit hook.
agentic.branch.delete action was already registered in prep.go; this lane
routes the actual delete behaviour through the new helper instead of
editing the registration site.
Sandbox blocked from go test by outer go.work conflicting replacements;
gofmt clean. Supervisor's clean workspace catches.
Co-authored-by: Codex <noreply@openai.com>
Closes tasks.lthn.sh/view.php?id=545
23f4be5b85