Epic-lead force — close the loop: orchestrator auto-executes flower:spawn-epic-lead (incl. epic branch/worktree provision) on a routed force brief (follow-up to #241)

Follow-up to #241 (merged). #241 shipped the deterministic ROUTING half: a force-pinned brief → AutoDispatchService emits a `routed_epic_lead` outcome carrying a ready `flower:spawn-epic-lead … --confirm` command, and creates NO plain dispatch_request. But the final loop-closure for TRUE hands-off (the operator's #241 decision = "auto-spawn, no hoping") is deferred: the orchestrator still has to run that command by hand. ## Deliverable Make the orchestrator AUTO-EXECUTE the routed epic-lead spawn end-to-end on pickup of a force-routed brief: - Provision the epic branch (`flower/epic-<id>`) + isolated worktree via the external worktree-manager (respecting the Brief #184 `WorktreePreparer` env-ready gate — flower's `worktrees` table is a discovery mirror, not a creator). - Invoke `flower:spawn-epic-lead --confirm` (registerExpected lead + SpawnDaemonBridge) so the lead boots into its epic worktree. - Keep a human-visible/confirm escape hatch, but default to hands-off per the #241 decision. ## Constraints / refs Additive; don't change the MAIN baton / single-master-merge invariant (the lead never holds the baton — #234). Test the auto-execute path with worktree-manager mocked (external Go CLI, can't run in sqlite tests). Interacts with #245 (coordination-drain resilience — the orchestrator drain is where this fires). Refs: #241 (routing hook), #226 (epic-lead spawn mechanism), #184 (WorktreePreparer), #235 (EpicLeadPolicy).