feat(FN-2170): add dev-server preview detection and log viewer flow

- Add dev-server port detection utilities and wire detected preview state into process/manager lifecycle
- Normalize dev-server status API responses with preview URL, detected port, and manual override compatibility
- Introduce useDevServerLogs and DevServerLogViewer, and integrate them into the DevServer dashboard view
- Expand dashboard test coverage for detection edges, process/routes behavior, log history handling, and CSS regressions

packages/dashboard/app/__tests__/dev-server-layout-css.test.ts

@@ -0,0 +1,48 @@
+import { readFileSync } from "node:fs";
+import { resolve } from "node:path";
+import { describe, expect, it } from "vitest";
+
+const css = readFileSync(resolve(__dirname, "../styles.css"), "utf-8");
+
+function getRule(selector: string, options: { last?: boolean } = {}): string {
+  const escapedSelector = selector.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+  const matches = [...css.matchAll(new RegExp(`${escapedSelector}\\s*\\{[^}]*\\}`, "g"))];
+  expect(matches.length, `Expected CSS rule for ${selector}`).toBeGreaterThan(0);
+
+  if (options.last) {
+    return matches[matches.length - 1]?.[0] ?? "";
+  }
+
+  return matches[0]?.[0] ?? "";
+}
+
+describe("Dev server view CSS layout regressions", () => {
+  it("keeps config and candidate lists scrollable with bounded height", () => {
+    const configRule = getRule(".dev-server-config");
+    expect(configRule).toContain("max-height: min(52vh, calc(var(--space-2xl) * 16))");
+    expect(configRule).toContain("overflow-y: auto");
+
+    const candidatesRule = getRule(".dev-server-candidates");
+    expect(candidatesRule).toContain("max-height: min(36vh, calc(var(--space-2xl) * 9))");
+    expect(candidatesRule).toContain("overflow-y: auto");
+  });
+
+  it("renders fullscreen log viewer above fixed chrome layers", () => {
+    const fullscreenRule = getRule(".devserver-log-viewer--fullscreen");
+    const zIndexMatch = fullscreenRule.match(/z-index:\s*(\d+)/);
+    expect(zIndexMatch).toBeTruthy();
+
+    const zIndex = Number.parseInt(zIndexMatch?.[1] ?? "0", 10);
+    expect(zIndex).toBeGreaterThan(50);
+  });
+
+  it("separates warning fallback styling from external-only mode", () => {
+    const fallbackRule = getRule(".dev-server-preview-fallback", { last: true });
+    const externalOnlyRule = getRule(".dev-server-preview-external-only", { last: true });
+
+    expect(fallbackRule).toContain("var(--color-warning)");
+    expect(externalOnlyRule).toContain("border: 1px solid var(--border)");
+    expect(externalOnlyRule).toContain("background: var(--surface)");
+    expect(externalOnlyRule).not.toContain("--color-warning");
+  });
+});