fix(freshness): hold checking state for 400ms minimum

Cached GitHub responses resolved so fast that the spinner state was
overwritten before Vue could render it, so clicking the badge from
"Not checked" looked like nothing happened.

src/hooks/useNoteFreshness.hook.ts

@@ -13,6 +13,8 @@ export type FreshnessStatus =
   | "outdated"
   | "offline"
 
+const MIN_SPINNER_MS = 400
+
 export const useNoteFreshness = ({
   user,
   repo,
@@ -38,15 +40,24 @@ export const useNoteFreshness = ({
   const check = async () => {
     if (!path.value) return
     status.value = "checking"
+    const startedAt = performance.now()
+
+    let next: FreshnessStatus
     const remoteSha = await fetchLatestSha(path.value)
     if (remoteSha === null) {
-      status.value = "offline"
-      return
+      next = "offline"
+    } else {
+      latestSha.value = remoteSha
+      lastCheckedAt.value = new Date()
+      const local = await expectedSha()
+      next = remoteSha === local ? "verified" : "outdated"
     }
-    latestSha.value = remoteSha
-    lastCheckedAt.value = new Date()
-    const local = await expectedSha()
-    status.value = remoteSha === local ? "verified" : "outdated"
+
+    const elapsed = performance.now() - startedAt
+    if (elapsed < MIN_SPINNER_MS) {
+      await new Promise((r) => setTimeout(r, MIN_SPINNER_MS - elapsed))
+    }
+    status.value = next
   }
 
   const pullLatest = async (): Promise<string | null> => {