Remove the Studio Overview view and land on Sessions

Traceability

• Spec ID: studio-remove-overview-view
• Status: in progress

Intent

Overview is the first View in the Studio sidebar and the default landing area, but it does not carry a decision the rest of the shell cannot already make:

• Its Recent Sessions pane is a truncated copy of the Sessions View, reached through one extra hop. Clicking a row navigates to Sessions anyway.
• Its Workspace summary facts (inputs, sessions, agents, artifacts, repository) restate the per-View status strings the sidebar already shows on every row, plus the status bar at the bottom of every View.
• Its Next Actions pane is a second rendering of the sidebar's View list.

So the landing surface of the workbench is a summary of the navigation next to it, and a reader must leave it before doing anything. Removing it makes Sessions — the retained evidence a reader actually opens Studio for — the landing View.

The Artifacts empty state has a related problem. When a Project is open and simply has no changed artifacts, the empty state still offers Open Another Project. Switching Projects is not the next step for that state, and the sidebar's Project switcher already owns that action. The same action remains correct in the disconnected Artifacts state, where it is the only way forward.

Non-goals

• Redesigning Sessions. It becomes the landing View unchanged, including its own disconnected empty state.
• Auditing openProjectAction in the other Views' empty states. In Inputs, Commits, Debugger, and Compare the empty state means "this Project cannot do this", where opening another Project is a real remedy. Only the Artifacts "no changed artifacts" state loses it.
• Persisting a per-reader landing View. The default stays a constant.

Acceptance criteria

• AC-1: Overview no longer appears in the sidebar View list, and overview is no longer a member of StudioArea.
• AC-2: Loading Studio with no route, an unknown route, or an unparsable Project route lands on Sessions, and the toolbar title and status bar report Sessions.
• AC-3: A stale #/overview or #/projects/<id>/overview hash resolves to Sessions rather than a blank work area, keeping the Project segment when it is present.
• AC-4: Roving tabindex over the View list still yields exactly one tab stop, and arrow keys move from the first row (Customizations) onward.
• AC-5: The Artifacts empty state for an open Project with an empty catalog renders no Open Another Project button. The Artifacts state for a Project that is not connected keeps its Open Project action.
• AC-6: No overview i18n namespace, area.overview label, destination.overviewStatus status, .control-overview / .overview-* rule, or studioOverview model code remains in the package. Unrelated usage-overview* (Inspector) and call-overview / overview-pair (Experiment) styles are untouched.
• AC-7: No console or page errors and no document-level horizontal overflow at 1440×900, 1024×768, and 390×844.

Plan

1. studio-shell-model.ts: drop "overview" from StudioArea, drop the overview destination, delete studioOverview and the StudioOverviewModel / StudioOverviewMode / StudioOverviewAction / StudioOverviewFact types, and export a STUDIO_DEFAULT_AREA constant.
2. project-routing.ts: fall back to STUDIO_DEFAULT_AREA instead of the hardcoded "overview", and resolve a known-but-removed area the same way.
3. App.tsx: delete the Overview component, its render branch, the overviewConfig derivation, and the overview entry in STUDIO_AREAS; resolve the active destination through STUDIO_DEFAULT_AREA.
4. ProjectSidebar.tsx: remove the overview icon mapping and the now-unused SquaresFour import.
5. i18n: delete en/overview.ts and zh-CN/overview.ts, unregister the namespace, and remove area.overview / destination.overviewStatus from both common.ts files.
6. shell.css: remove the Overview block and its narrow-layout overrides.
7. ArtifactsWorkspace.tsx: stop passing openProjectAction into the "no changed artifacts" empty state.
8. Tests: delete test/browser/overview.spec.mjs, drop the studioOverview suites from test/studio-shell-model.test.ts, retarget the routing default in test/studio-project.test.ts, and update the landing assertions in tool-call, language, project-shell, and artifact-host browser specs.
9. packages/harness-studio/README.md: correct the View list.

Test and review evidence

• npm run typecheck and npx vitest run in packages/harness-studio.
• npx playwright test test/browser/project-shell.spec.mjs test/browser/tool-call.spec.mjs test/browser/language.spec.mjs for the landing View, roving focus, and locale title.
• npx playwright test test/browser/artifact-host.spec.mjs for the Artifacts empty state and the post-open route.
• Screenshots at the three review widths.

Risk

• Stale bookmarks and Electron deep links. Any retained #/overview hash must not strand the reader. parseStudioLocation already returns the default for an unknown area, so the removal turns those routes into Sessions; AC-3 covers it explicitly.
• Default-area drift. Two places pick a landing View (hash parsing and the destination lookup in App.tsx). They are unified on one exported constant so the sidebar order can change without silently moving the landing View.
• Test coupling. Roughly a dozen browser assertions locate the landing View by the heading Overview. They are retargeted rather than relaxed, so a regression that lands on the wrong View still fails.