fix(tangent): stop the tab strips scrolling up and down

[camielvs]

A workarea with enough tabs open grew a vertical scrollbar inside a bar one tab tall.

Cause

Both tab strips ask only for overflow-x-auto. But a box with one axis set to anything other than visible computes the other axis to auto — so overflow-y became auto too. The horizontal scrollbar then eats into the strip's fixed h-9, the tabs overflow downwards by the height of their own scrollbar, and the strip grows a second scrollbar to reach them.

Fix

One named class, SCROLLING_TAB_STRIP, carrying both axes and the reason, used by both strips. The chat strip had the same fault and the same fix — it just needs more tabs before it shows.

Testing

pnpm run validate and npx vitest run green (3079 tests). No new test: the only thing to assert is a class string, which would be a change-detector rather than a check that the bug is gone.

Verified in a browser with five documents open at 760px, where the strip genuinely overflows:

overflowX: "auto"   overflowY: "hidden"
scrollWidth: 988    clientWidth: 959     (still scrolls sideways)

One honest caveat: headless Chromium draws overlay scrollbars, which take no layout width, so the visible scrollbar in the original report cannot be reproduced there by measurement. What is verified is that the computed overflow-y was auto before and is hidden now, and that horizontal scrolling still works — and hidden cannot produce a vertical scrollbar.

🤖 Generated with Claude Code

[github-actions]

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A preview build has been created at: 09-21-fix_workarea_tabs_scroll_sideways/679d9ae

[camielvs]

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• fix(runs): say why the backend refused a run instead of that it did #2794 : 2 dependent PRs (#2796 , #2798 )
• feat(tangent): brief the agent on naming, and on the project its runs belong to #2792
• feat(projects): fix cancelling, track shared projects, flag unreachable pipelines #2790
• feat(tangent): keep an agent's edits in frame on the canvas #2789
• feat(tangent): bring Tangent onto the dashboard #2787
• feat(tangent): show a project's runs on the tangent page #2786
• fix(projects): show an agent's run on the project it belongs to #2785
• fix(agent): submit a spec that came from the editor's store #2784
• chore: increase max turns in remote agent #2779
• fix(tangent): stop the tab strips scrolling up and down #2777 👈 (View in Graphite)
• feat(projects): make the agents' instructions a project document #2776
• feat(tangent): list the pipelines the backend holds #2775
• feat(projects): show a project's documents on both pages #2774
• fix(tangent): project window parity — share, new-session links, agent-created pipelines, and a folded-away project window #2773
• refactor(projects): describe a project's resources one way #2765
• feat(projects): delete and share a project from either page #2764
• feat: open a new project ready to work in #2763
• feat: let the project page and Tangent reach each other #2762
• fix: keep a long project name inside the tile it belongs to #2761
• feat: say so when Tangent cannot be reached #2760
• feat: open a project where the work happens #2759
• feat: run a pipeline inside a project #2754
• feat: add pipelines held in this browser to a project #2745
• feat: project page #2738
• feat: create a project from a tile in the grid #2735 : 2 other dependent PRs (#2736 , #2737 )
• feat: projects dashboard #2734
• chore: tangent - annotate runs submission to projectid #2758
• fix: tangent - proper debug sequence system prompt #2757
• fix: tangent - quick run button from mini content window #2744
• fix: tangent - remote agent send delta immediately #2743
• fix: tangent - mint proper authorization with tangent #2742
• feat: tangent - debug in tangent sequence #2741
• chore: add autolayout tool #2740
• feat: tangent - resource management via document entity #2733
• feat: tangent - interactive chips in tangent chat #2732
• chore: save id stack to replay ids on reloads #2731
• refactor: tangent - migrate tangetproectcontext onto mobx #2730
• feat: tangent - keep track of open tabs while switching sessions inside project #2729
• feat: tangent - remote agent for runview and editor #2728
• refactor: tangent - structured workarea target #2727
• feat: tangent - embedded pipeline run view #2726
• feat: tangent - embedded pipeline editor #2725
• feat: tangent - dynamic workarea remote tools #2724
• feat: tangent - resources management in project view #2723
• feat: tangent project view page #2722
• feat: workspaces and projects service #2720
• chore: api client for workspaces and projects #2719
• master

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