test(ui): prove nested overlays through the production shadow seam

[cameronapak]

Summary

Validates YPE-5355 through the production integration seam (ShadowRootHost with portalStrategy="local-top-layer" + real VerseActionPopover, HighlightPermissionDialog, Dialog, and Popover). This is proof and contract only. YPE-5356 owns any runtime ship to main.

This work is possible because of PR #375 by Austin Harms (abharms). That PR carefully researched and proved a proposed root-owned LIFO overlay-ownership registry, with four independent reviews agreeing the ShadowRoot + React portal architecture is justified. This draft does not replace or correct that research. It asks the open follow-up question: does the current production seam already handle the ticket scenarios without a new ownership registry?

Finding

No ownership registry was added. The production seam already handled the required scenarios. One small adapter-side gap appeared and was fixed in the existing focus helper.

Scenario	Result
popover → dialog (VerseActionPopover opening HighlightPermissionDialog)	Pass. YPE-1034: the verse-action popover may remain open. Both live in the real [data-yv-shadow-local-overlay] container.
dialog → popover (production Dialog launching production Popover)	Pass. Nested popover mounts in the same container, stays clickable, and can hold focus.
two independent overlays	Pass. Current Radix dismiss-on-outside is kept; both staying mounted is not required.
rapid close/reopen during unequal exit	Pass after a small adapter fix. Reopen during exit had captured the outgoing overlay as the restore target, leaving ShadowRoot.activeElement empty.
cleanup / unmount while a modal is open	Pass. Host teardown is idempotent and does not crash.
second isolated ShadowRoot	Pass. Each island owns its own top-layer container.

What changed

• Chromium Storybook proof: packages/ui/src/components/shadow-overlay-production-seam.shadow-isolation.stories.tsx
• Static visual frames of the same production harness (not tagged integration)
• Production focus helper: skip portal-container nodes when choosing a restore target; fall back to the last wrapper control
• ADR 0006 + isolation plan: record that YPE-5355 did not need a new ownership registry; YPE-5356 owns shipping
• Empty changeset (no package release)

Complexity deliberately avoided

No second mutable ownership class, parentId graph, custom exiting phase, manual revision bookkeeping, duplicated focus trap, or fatal lifecycle throws. Escape, outside dismissal, presence, and focus scope stay with Radix. Focus acceptance stays in the adapter.

Out of scope

• Touching, commenting on, closing, approving, merging, or marking ready PR feat(ui): prove nested and concurrent Shadow DOM overlay behavior (YPE-5355) #375
• Firefox, WebKit, AT matrix
• Nested shadow-root-inside-overlay
• Shipping overlay wiring to main (YPE-5356)

Jira

YPE-5355

  

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[cameronapak]

Review

No Jira. Spec is the Conductor off-ticket showcase (related YPE-5355).

Summary

Standards: 0 must-fix. Worst: none.

Spec: 0 must-fix on this SHA. Worst: none.

CI: pass.

I would approve the code. This UI proof still needs Cam's visual review. Stay draft. The PR has no image artifacts, so add before-and-after screenshots with before-and-after.

For Agents: pin and review state

• Pin HEAD: da7e47df167f464a12b0dc246af3f1e5a0f25da8
• Base branch: journey-to-the-shadow-dom
• Draft: yes. Stay draft. No ready, APPROVE, or merge.
• Event: COMMENT only (UI overlay + Cam-authored PR).
• Spec source: Conductor off-ticket showcase. Do not rewrite Austin's YPE-5355 ticket. Do not touch PR #375.
• Greptile: missing (ok).
• CI: Build, Bundle Size, Integration Tests, Lint, Lint Commit Messages, Lint PR Title, Locale Ownership, Test, Type Check, i18n Check, Require Changeset pass. Publish coverage badges skipped.
• Finding: no ownership registry; production seam covers required scenarios; rapid-reopen restore gap fixed in use-shadow-dialog-focus.ts via useShadowFocusRestoreTarget.
• Non-blocking nits: independent-overlays path does not assert Radix outside-dismiss closed the verse popover; portal restore skip is broad (!container.contains) and untested on YPE-1034 close path.

By Code Reviewer bot, sent on behalf of Cam.