FN-6809: fix dashboard nav CSS tokens

Align dashboard navigation styling and tests with defined spacing and status tokens.

- Replace undefined sidebar CSS tokens with defined dashboard values while preserving circular and todo-active styling.
- Update the mobile nav touch-target test to assert the tokenized 36px minimum height.
- Add FNXC comments documenting the token requirements behind the fixes.

Files changed:
 packages/dashboard/app/__tests__/mobile-nav-bar-css.test.ts |  3 ++-
 packages/dashboard/app/components/LeftSidebarNav.css        | 12 ++++++++++--
 2 files changed, 12 insertions(+), 3 deletions(-)

Fusion-Task-Id: FN-6809

Fusion-Task-Lineage: 43ddb9cb-5ead-4289-9254-6c0fa5c3af40

packages/dashboard/app/__tests__/mobile-nav-bar-css.test.ts

@@ -52,7 +52,8 @@ describe("mobile-nav-bar.css", () => {
 
   it("tab touch targets are at least 36px", () => {
     const block = extractRuleBlock(cssContent, ".mobile-nav-tab");
-    expect(block).toContain("min-height: 36px");
+    // FNXC:DashboardStyling 2026-06-20-20:56: FN-6809 keeps the 36px touch-target intent via tokens; --space-xl (24px) + --space-md (12px) resolves to the same min-height.
+    expect(block).toContain("min-height: calc(var(--space-xl) + var(--space-md))");
   });
 
   it("footer-aware positioning keeps nav at bottom: 0 when footer is visible", () => {

packages/dashboard/app/components/LeftSidebarNav.css

@@ -29,6 +29,10 @@ The left sidebar is a sibling of project-content, so it does not inherit project
   flex-shrink: 0;
 }
 
+/*
+FNXC:DashboardStyling 2026-06-20-20:56:
+The floating sidebar collapse toggle must stay fully round, but FN-6809 surfaced that --radius-full is not a defined dashboard token. Use 50% here to preserve the circular affordance without introducing another undefined custom property.
+*/
 .left-sidebar-nav__collapse-toggle--floating {
   position: absolute;
   top: var(--space-sm);
@@ -40,7 +44,7 @@ The left sidebar is a sibling of project-content, so it does not inherit project
   min-width: calc(var(--space-lg) + var(--space-md));
   min-height: calc(var(--space-lg) + var(--space-md));
   padding: var(--space-xs);
-  border-radius: var(--radius-full);
+  border-radius: 50%;
   box-shadow: var(--shadow-sm);
 }
 
@@ -96,8 +100,12 @@ The left sidebar is a sibling of project-content, so it does not inherit project
   box-shadow: var(--focus-ring);
 }
 
+/*
+FNXC:DashboardStyling 2026-06-20-20:56:
+The active sidebar item must use the defined --status-todo-bg token so the dashboard CSS token-validity gate stays green. FN-6809 replaces the undefined --todo-bg reference without changing the rendered todo status treatment.
+*/
 .left-sidebar-nav__item--active {
-  background: var(--todo-bg);
+  background: var(--status-todo-bg);
   color: var(--todo);
 }