#17604 cmux-next: Back returns to the New Tab page after a jump

Summary

After jumping from the New Tab page to a tab, Back now returns to the New Tab page.

The location trail steps only between workspaces by default, so a jump to a tab in the same workspace replaced the New Tab page's entry instead of adding one. A jump made soon after the page opened was also merged into it as a quick sweep. A jump picked in the New Tab location bar now records its own step (LocationTrail.recordJump, armed by LocationTrailService.noteJump from NewTabPage.jump).

Opening a recent chat from the page's cards still turns the page into that chat in place, in the same tab. Back does not undo that, since no other tab is involved.

Testing

• Failing tests first (d4747ac9d75): LocationTrailJumpTests, LocationTrailWiringTests.aNewTabJumpInsideTheWorkspaceIsABackStep.

Changelog

• Fixed: Back returns to the New Tab page after jumping from it to another tab.

🤖 Generated with Claude Code

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Summary by cubic

Fixes Back navigation from the New Tab page: a tab picked from its location bar is now its own step on the location trail, even inside the same workspace and right after the page opened, so Back returns to the New Tab page.

Opening a recent chat from the page's cards is unchanged: it turns the page into that chat in place, and Back does not undo it.