feat(workspace): the console tab bar is the session view's only header

The status/name/back-arrow row is gone; Tools sits at the tab bar's right
end and the pipeline/feature pickers show only with a template.
LaneConsolePane is reduced to the terminal (no title, no Active runs, no
New run): RunHistory.tsx, api.run.history and the page's active-sessions
poll are removed.

client/src/pages/__tests__/Workspace.changesPanel.test.tsx

@@ -69,7 +69,6 @@ vi.mock("../../lib/api", async (importOriginal) => {
     api: {
       run: {
         list: r({ items: [] }),
-        history: r({ items: [] }),
         binary: r({ found: true, path: "/usr/bin/claude" }),
         cwds: r({ items: [HOME] }),
         files: r({ items: [] }),