feat: fast note open — use allContent cache to skip IPC disk reads

handleSelectNote and handleReplaceActiveTab now check the in-memory
allContent cache before issuing a Tauri IPC call. Cache hits open the
tab synchronously (zero latency). Cache misses fall back to the disk
read and populate allContent via onContentLoaded so subsequent opens
of the same note are instant.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/hooks/useNoteActions.ts

@@ -36,6 +36,8 @@ export interface NoteActionsConfig {
   markContentPending?: (path: string, content: string) => void
   /** Called after a new note is persisted to disk (e.g. to refresh git status for Changes view). */
   onNewNotePersisted?: () => void
+  /** Return cached content for a path (from allContent), or undefined on cache miss. */
+  getCachedContent?: (path: string) => string | undefined
 }
 
 async function performRename(
@@ -326,7 +328,10 @@ async function runFrontmatterAndApply(
 
 export function useNoteActions(config: NoteActionsConfig) {
   const { addEntry, removeEntry, updateContent, entries, setToastMessage, updateEntry, addPendingSave, removePendingSave } = config
-  const tabMgmt = useTabManagement()
+  const tabMgmt = useTabManagement({
+    getCachedContent: config.getCachedContent,
+    onContentLoaded: updateContent,
+  })
   const { setTabs, handleSelectNote, openTabWithContent, handleCloseTab, handleCloseTabRef, activeTabPathRef, handleSwitchTab } = tabMgmt
   const tabsRef = useRef(tabMgmt.tabs)
   // eslint-disable-next-line react-hooks/refs