Function cleanup_failed_promote_orphan 

fn cleanup_failed_promote_orphan(state: &Arc<AppState>, label: &str)

Phase B.5c follow-up — clean up an orphan pool window left behind when promote_pool_window’s HWND validation fails. Without this, the popped label sits in state.browsers but is no longer in unpromoted_pool_labels (promote removed it) and never became a real user window (no WindowOpened was reported). Host’s compute_and_report_host_counts then counts it as a window, while the launcher mirror correctly does not — persistent off-by-one drift. (Caught by B.4b drift detection during B.5c smoke test on v0.33.461.)

Contract: this fn is responsible for ALL recovery including pool refill. The caller MUST NOT call spawn_pool_window itself — double refill would overshoot POOL_TARGET_SIZE and waste renderer capacity. (codex P1 PR #582 round-1.)

Two paths:

• Graceful path (browser+host alive in CEF): issue close_browser(1) and let CEF’s on_before_close fire. That path runs the standard cleanup chain — drops from state.browsers + window_meta, calls on_pool_window_destroyed (which itself triggers refill via spawn_pool_window when pool size is below target), and triggers compute_and_report_host_counts from client.rs.
• Direct path (browser or host already gone): on_before_close won’t fire so we do its job inline — drop from browsers + window_meta, send report_window_closed (silent no-op in launcher reducer for an unknown label), spawn the refill ourselves, and emit a drift count snapshot so the orphan’s removal is observable on the same tick. (reagent P2 PR #582 round-1 — original direct path skipped the snapshot.)