test: hit-test the browser portal tab strip with its own click

[teamleaderleo]

Summary

WindowBrowserHostViewTests.testHostViewPassesThroughUnderlyingTabStripInSecondWindowBelowTitlebarBand fails on main when other suites run first in the same app host (for example run 36326938624, app-host shard 5/7). When it runs alone it passes (run 36332446194).

The test calls hitTest(_:), which routes on the ambient NSApp.currentEvent. A probe run that logged it before the assertions (36334701691) found a real MouseEntered for another suite's window (winNum=19820). Hover events check only registered tab-bar regions (BonsplitTabBarPassThrough.usesRegisteredTabBarRegionsOnly), so the test's unregistered fake strip was not passed through. Real minimal-mode tab strips register their regions, and clicks still use the fallback, so the product behaves as designed. The test just never said which event it meant.

The first commit reproduces the failure deterministically: it leaves a stale mouseEntered for another window as NSApp.currentEvent, which is what the probe found. The second commit makes the test hit-test with its own left-mouse-down for each window and a private drag pasteboard, through performHitTest(at:currentEvent:dragPasteboard:), as the sibling Dock divider tests already do. The stale hover stays in the test as a guard.

Testing

Focused runs through scripts/run-e2e.sh on the owned mini lane (glaeda-std-xcode-26.6). I checked each log to confirm the test executed:

Commit	Selection	Result
d762999 (main c842f7d + logging)	the test's suite plus 5 XCTest suites that precede it in shard 5	failed at both assertions, currentEvent = MouseEntered
9c41d18 (regression)	the test alone	failed at both assertions (1494, 1498)
a938445 (fix)	the test alone	passed
a938445 (fix)	the same shard-5 composition, 105 XCTests	passed

The composition is a subset of the shard, because run-e2e.sh caps its concurrency group at 400 characters. Its selectors are BrowserSessionHistoryRestoreTests, BrowserWindowPortalLifecycleTests, TerminalWindowPortalLifecycleTests, TabManagerReopenClosedBrowserFocusTests, TerminalNotificationCallerTests and WindowBrowserHostViewTests. Whether a stray hover event arrives depends on where the pointer sits, so this composition doesn't always fail on main: 36334723121 at badf9f6 passed. That's why the regression commit sets the event explicitly.

Changelog

none

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📥 Commits

Reviewing files that changed from the base of the PR and between 8efe28d and a938445.

📒 Files selected for processing (1)

• cmuxTests/BrowserPanelTests.swift

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[github-actions]

Merge receipt for a9384455c4: every check was green at merge (16 verified; 14 skipped by policy). Full suite runs on main after merge.