feat(notes): banner when viewing an older shared version

Cache the note path on each snapshot so an old shared sha can find its
current version, and show a calm "older shared version — View latest"
banner. The exact snapshot is shown as-is; the banner only offers a jump
to the latest, never swapping content.

src/hooks/useFile.hook.ts

@@ -2,6 +2,7 @@ import { computed, Ref, ref, toValue } from "vue"
 
 import { markdownBuilder } from "@/hooks/useMarkdown.hook"
 import { prepareNoteCache } from "@/modules/note/cache/prepareNoteCache"
+import { latestShaIfOlder } from "@/modules/note/snapshotStatus"
 import { queryFileContent } from "@/modules/repo/services/repo"
 import { useUserRepoStore } from "@/modules/repo/store/userRepo.store"
 
@@ -14,6 +15,16 @@ export const useFile = (sha: Ref<string> | string, retrieveContent = true) => {
     return file?.path
   })
 
+  // Path recovered from the cached note doc — lets us locate the latest version
+  // even when this (old) sha is no longer in store.files.
+  const cachedNotePath = ref<string | undefined>()
+
+  // When viewing an older snapshot of a known note, the note's current sha
+  // (null when already viewing the latest).
+  const newerSha = computed(() =>
+    latestShaIfOlder(shaValue, path.value ?? cachedNotePath.value, store.files)
+  )
+
   const {
     render,
     renderFromUTF8,
@@ -47,6 +58,8 @@ export const useFile = (sha: Ref<string> | string, retrieveContent = true) => {
     fromCache.value = !!cachedNote
 
     if (cachedNote) {
+      cachedNotePath.value = cachedNote.path ?? cachedNotePath.value
+
       if (from === "path") {
         queryFileContent(store.user, store.repo, shaValue).then(
           (fileContent) => {
@@ -104,6 +117,7 @@ export const useFile = (sha: Ref<string> | string, retrieveContent = true) => {
 
   return {
     path,
+    newerSha,
     content,
     rawContent,
     getRawContent,