chore(backlog): capture overlay_window findings in TASK-20 breakdown

backlog/tasks/task-20.4 - Implement-dedicated-secondary-top-bar-overlay-window.md

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+---
+id: TASK-20.4
+title: Implement dedicated secondary top-bar overlay window
+status: To Do
+assignee: []
+created_date: '2026-02-12 09:43'
+labels: []
+dependencies: []
+parent_task_id: TASK-20
+priority: medium
+---
+
+## Description
+
+<!-- SECTION:DESCRIPTION:BEGIN -->
+Create and integrate a dedicated secondary subtitle overlay window with independent lifecycle, z-order, bounds, and pointer policy, decoupled from primary visible/invisible overlay windows.
+<!-- SECTION:DESCRIPTION:END -->
+
+## Acceptance Criteria
+<!-- AC:BEGIN -->
+- [ ] #1 A third overlay window dedicated to secondary subtitles is created and managed alongside existing visible/invisible windows.
+- [ ] #2 Secondary window visibility follows secondary mode semantics (`hidden`/`visible`/`hover`) independent of primary overlay visibility.
+- [ ] #3 Secondary subtitle text/mode/style updates are routed directly to the secondary window renderer path.
+- [ ] #4 Pointer passthrough/interaction behavior for secondary window is explicit and does not regress existing hover/selection interactions.
+- [ ] #5 Window cleanup/lifecycle (create, close, restore) integrates with existing overlay runtime lifecycle.
+<!-- AC:END -->