feat(notes): share an always-latest link, not just a snapshot

The Share button now offers two links: the pinned snapshot (default) and
an "always latest" link that carries note paths in `?liveNotes` instead of
blob shas. On open they resolve to the current shas against the HEAD file
list and the URL is rewritten to the ordinary pinned form, so freshness,
editing and the snapshot banner keep working unchanged.

src/hooks/useResolveLiveNotes.hook.ts

@@ -0,0 +1,50 @@
+import { watch } from "vue"
+import { useRoute, useRouter } from "vue-router"
+
+import { resolveLivePathsToShas } from "@/modules/note/liveNotes"
+import { useUserRepoStore } from "@/modules/repo/store/userRepo.store"
+
+// A living link (`?liveNotes=path&liveNotes=path`) carries file paths instead of
+// pinned blob shas. On open we resolve each path to the latest sha against the
+// HEAD file list and rewrite the URL to the ordinary pinned `stackedNotes` form
+// — so the recipient lands on the current version, and from there everything
+// (freshness, editing, the snapshot banner) behaves exactly as a shared snapshot
+// would. The rewrite is a `replace`, so no history entry and no view transition.
+export const useResolveLiveNotes = (onResolved?: () => void) => {
+  const route = useRoute()
+  const router = useRouter()
+  const store = useUserRepoStore()
+
+  let resolved = false
+
+  const tryResolve = () => {
+    if (resolved) return
+
+    const raw = route.query.liveNotes
+    if (!raw) {
+      resolved = true
+      return
+    }
+
+    // Wait for the HEAD file list before resolving paths to shas.
+    if (store.files.length === 0) return
+    resolved = true
+
+    const entries = (Array.isArray(raw) ? raw : [raw]).filter(
+      (entry): entry is string => typeof entry === "string"
+    )
+    const shas = resolveLivePathsToShas(entries, store.files)
+
+    const query = { ...route.query }
+    delete query.liveNotes
+    if (shas.length) {
+      query.stackedNotes = shas
+    } else {
+      delete query.stackedNotes
+    }
+
+    router.replace({ path: route.path, query }).then(() => onResolved?.())
+  }
+
+  watch(() => store.files.length, tryResolve, { immediate: true })
+}