Module panes 

Browser pane lifecycle (Phase H.1) reducer handlers. Extracted from reducer/mod.rs in task #182 PR-F-2 for navigability.

Functions

handle_abort_browser_pane_create 🔒

handle_complete_browser_pane_close 🔒

handle_complete_browser_pane_create 🔒

handle_drain_browser_pane_by_label 🔒

PR #5 — sole label-keyed drain entry point. Replaces pane::lifecycle::PaneStateMachine::drain_by_label.

handle_enqueue_browser_pane_close 🔒

handle_enqueue_browser_pane_create 🔒

handle_try_register_browser_pane_live 🔒

PR #5 — sole pane registration entry point. Replaces pane::lifecycle::PaneStateMachine::try_register_live.