FN-5934: replace undefined dashboard spacing token

Replace dashboard CSS uses of the undefined --space-2xs token with supported spacing values.

- swap var(--space-2xs) for var(--space-xs) in confirm dialog, merge advance notice, and PR checks styles
- add a dashboard test that scans component stylesheets for undefined --space-2xs references
- assert shared token sources continue to omit an intentional --space-2xs definition

Files changed:
 .../app/__tests__/space-token-defined.test.ts      | 45 ++++++++++++++++++++++
 .../dashboard/app/components/ConfirmDialog.css     |  2 +-
 .../app/components/MergeAdvanceNotice.css          |  8 ++--
 packages/dashboard/app/components/PrChecksList.css |  2 +-
 4 files changed, 51 insertions(+), 6 deletions(-)

Fusion-Task-Id: FN-5934

Fusion-Task-Lineage: aa77df19-3f76-4ede-aa42-0396230edde5

packages/dashboard/app/__tests__/space-token-defined.test.ts

@@ -0,0 +1,45 @@
+import { readdirSync, readFileSync } from "node:fs";
+import { join, resolve } from "node:path";
+import { describe, expect, it } from "vitest";
+
+const appDir = resolve(__dirname, "..");
+const componentsDir = resolve(appDir, "components");
+const stylesPath = resolve(appDir, "styles.css");
+const themeDataPath = resolve(appDir, "public/theme-data.css");
+
+function listComponentCssFiles(): string[] {
+  return readdirSync(componentsDir)
+    .filter((name) => name.endsWith(".css"))
+    .sort();
+}
+
+describe("dashboard spacing token hygiene", () => {
+  it("does not reference undefined --space-2xs in any component stylesheet", () => {
+    const violations: string[] = [];
+
+    for (const fileName of listComponentCssFiles()) {
+      const filePath = join(componentsDir, fileName);
+      const source = readFileSync(filePath, "utf8");
+      const lines = source.split(/\r?\n/);
+
+      for (let index = 0; index < lines.length; index += 1) {
+        if (lines[index].includes("var(--space-2xs)")) {
+          violations.push(`${fileName}:${index + 1}:${lines[index].trim()}`);
+        }
+      }
+    }
+
+    expect(violations).toEqual([]);
+  });
+
+  it("documents that --space-2xs remains intentionally undefined in shared token sources", () => {
+    const tokenSources = [
+      { name: "styles.css", source: readFileSync(stylesPath, "utf8") },
+      { name: "theme-data.css", source: readFileSync(themeDataPath, "utf8") },
+    ];
+
+    for (const { name, source } of tokenSources) {
+      expect(source).not.toContain("--space-2xs:");
+    }
+  });
+});

packages/dashboard/app/components/ConfirmDialog.css

@@ -12,7 +12,7 @@
 
 .confirm-dialog__checkbox {
   display: grid;
-  gap: var(--space-2xs);
+  gap: var(--space-xs);
   margin: 0 var(--space-xl) var(--space-lg);
 }
 

packages/dashboard/app/components/MergeAdvanceNotice.css

@@ -79,8 +79,8 @@
 .merge-advance-notice__push-advanced label {
   display: inline-flex;
   align-items: center;
-  gap: var(--space-2xs);
-  margin-top: var(--space-2xs);
+  gap: var(--space-xs);
+  margin-top: var(--space-xs);
 }
 
 .merge-advance-notice__push-error {
@@ -88,8 +88,8 @@
 }
 
 .merge-advance-notice__push-error pre {
-  margin: var(--space-2xs) 0;
-  padding: var(--space-2xs);
+  margin: var(--space-xs) 0;
+  padding: var(--space-xs);
   border-radius: var(--radius-sm);
   background: color-mix(in srgb, var(--color-error) 12%, transparent);
   color: var(--color-error);

packages/dashboard/app/components/PrChecksList.css

@@ -111,7 +111,7 @@
   border-radius: var(--radius-sm);
   color: var(--color-error);
   justify-content: center;
-  padding: var(--space-2xs) var(--space-sm);
+  padding: var(--space-xs) var(--space-sm);
 }
 
 .pr-checks__details-link--failing:hover {