fix: make 'b' shortcut route-aware to match hamburger behavior

On sessions route, 'b' toggles the sidebar. On other routes, 'b'
navigates back to sessions and opens the sidebar, matching the
hamburger button's context-aware behavior.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 0xjjjjjj

frontend/src/lib/utils/keyboard.test.ts

@@ -9,6 +9,7 @@ import {
 import { ui } from "../stores/ui.svelte.js";
 import { sessions } from "../stores/sessions.svelte.js";
 import { starred } from "../stores/starred.svelte.js";
+import { router } from "../stores/router.svelte.js";
 import { registerShortcuts } from "./keyboard.js";
 
 function fireKey(
@@ -283,7 +284,8 @@ describe("registerShortcuts", () => {
   });
 
   describe("b shortcut (toggle sidebar)", () => {
-    it("should toggle sidebar open/closed", () => {
+    it("should toggle sidebar on sessions route", () => {
+      router.navigate("sessions");
       ui.sidebarOpen = true;
       fireKey("b");
       expect(ui.sidebarOpen).toBe(false);
@@ -292,14 +294,24 @@ describe("registerShortcuts", () => {
       expect(ui.sidebarOpen).toBe(true);
     });
 
+    it("should navigate to sessions on non-session routes", () => {
+      router.navigate("insights");
+      ui.sidebarOpen = false;
+      fireKey("b");
+      expect(router.route).toBe("sessions");
+      expect(ui.sidebarOpen).toBe(true);
+    });
+
     it("should not toggle sidebar when modal is open", () => {
+      router.navigate("sessions");
       ui.sidebarOpen = true;
       ui.activeModal = "shortcuts";
       fireKey("b");
       expect(ui.sidebarOpen).toBe(true);
     });
 
     it("should not toggle sidebar when input is focused", () => {
+      router.navigate("sessions");
       ui.sidebarOpen = true;
       const input = document.createElement("input");
       document.body.appendChild(input);

frontend/src/lib/utils/keyboard.ts

@@ -204,7 +204,15 @@ export function registerShortcuts(
       "?": () => {
         ui.activeModal = "shortcuts";
       },
-      b: () => ui.toggleSidebar(),
+      b: () => {
+        if (router.route === "sessions") {
+          ui.toggleSidebar();
+        } else {
+          sessions.deselectSession();
+          router.navigate("sessions");
+          ui.sidebarOpen = true;
+        }
+      },
     };
 
     const action = keyActions[e.key];