feat(workspace): split menus start AI tools; drop the Tools menu

A pane's split right/down menus offered only New terminal. They now list
the same AI tools as the tab bar's + menu (newTabTools/newTabBody,
shared from ConsoleTabs), started bare in the first free slot on that
side of the pane.

The tab bar's Tools menu is gone: its readme run hit 409 ERUNLIVE
whenever slot 0 was live (always, in the session view) and depended on
a personal skill; MCP sync and the dev-sync check served the dormant
ship-feature-lane pipeline. The sidebar row menu's readme item goes too.
The routes stay, reached by `agenthub lanes mcp sync` and
`agenthub lanes sync-base`.

Also: the home's Memory header and file tabs no longer shrink (a long
file squeezed the tab row and clipped it).

client/src/components/__tests__/WorkspaceTree.test.tsx

@@ -459,20 +459,18 @@ describe("WorkspaceTree", () => {
     expect(screen.getByTestId("workspace-session-s-y")).toBeInTheDocument();
   });
 
-  it("offers Reset only on a managed workspace and the readme run only on claude", async () => {
+  it("offers Reset only on a managed workspace", async () => {
     const user = userEvent.setup();
     renderTree();
     await user.click(await screen.findByTestId("workspace-menu-1"));
     let menu = screen.getByTestId("workspace-row-menu-1");
     expect(within(menu).queryByText("Reset worktree…")).toBeNull();
-    expect(within(menu).getByText("Create/update readme file")).toBeInTheDocument();
     expect(within(menu).getByText("Delete workspace…")).toBeInTheDocument();
     await user.keyboard("{Escape}");
 
     await user.click(screen.getByTestId("workspace-menu-3"));
     menu = screen.getByTestId("workspace-row-menu-3");
     expect(within(menu).getByText("Reset worktree…")).toBeInTheDocument();
-    expect(within(menu).queryByText("Create/update readme file")).toBeNull();
   });
 });