perf: SFTP directory listing cache

- Added dirCache map to sftpPane for caching directory listings
- Cache hit: instant navigation (no disk/network I/O)
- Cache miss: read from disk/SFTP, store in cache per path
- R key clears current directory cache and forces fresh read
- Significant speedup when navigating back to previously visited folders

CHANGELOG.md

@@ -39,6 +39,13 @@
 - Stacked: `maxH = t.height - 6`; Side-by-side: `maxH = t.height - 5`
 - Breakpoints: compact (<60), medium (60–100), wide (≥100)
 
+### SFTP Performance Fix
+- Added directory listing cache (`dirCache map[string][]os.FileInfo`) to each pane
+- Cache hit: instant navigation (no disk/network call)
+- Cache miss: read from disk/SFTP, store in cache
+- `R` key now clears cache for current directory and forces re-read
+- Cache is per-path: navigating to a previously visited folder is instant
+
 ## v1.0.0 (2025-01-30)
 
 ### Added

pkg/tui/sftp_browser_tab.go

@@ -38,6 +38,9 @@ type sftpPane struct {
 	filterMode bool
 	filter     string
 
+	// Directory listing cache: path → entries
+	dirCache map[string][]os.FileInfo
+
 	// Remote only
 	sftpClient *sftp.Client
 
@@ -83,9 +86,11 @@ func NewSFTPBrowserTab(host *models.Host, dataDir string) *SFTPBrowserTab {
 		left: sftpPane{
 			cwd:       home,
 			localRoot: home,
+			dirCache:  make(map[string][]os.FileInfo),
 		},
 		right: sftpPane{
 			cwd:      "/",
+			dirCache: make(map[string][]os.FileInfo),
 		},
 		filterInput: fi,
 	}
@@ -154,10 +159,22 @@ func (t *SFTPBrowserTab) connect() {
 func (t *SFTPBrowserTab) refreshLocal() {
 	t.mu.Lock()
 	p := &t.left
-	p.entries = nil
+	cwd := p.cwd
 	t.mu.Unlock()
 
-	entries, err := os.ReadDir(p.cwd)
+	// Check cache first
+	t.mu.Lock()
+	if cached, ok := p.dirCache[cwd]; ok {
+		p.entries = cached
+		if p.selIdx >= len(cached) {
+			p.selIdx = 0
+		}
+		t.mu.Unlock()
+		return
+	}
+	t.mu.Unlock()
+
+	entries, err := os.ReadDir(cwd)
 	if err != nil {
 		return
 	}
@@ -178,6 +195,7 @@ func (t *SFTPBrowserTab) refreshLocal() {
 	})
 
 	t.mu.Lock()
+	p.dirCache[cwd] = infos
 	p.entries = infos
 	if p.selIdx >= len(infos) {
 		p.selIdx = 0
@@ -196,6 +214,18 @@ func (t *SFTPBrowserTab) refreshRemote() {
 		return
 	}
 
+	// Check cache first
+	t.mu.Lock()
+	if cached, ok := p.dirCache[cwd]; ok {
+		p.entries = cached
+		if p.selIdx >= len(cached) {
+			p.selIdx = 0
+		}
+		t.mu.Unlock()
+		return
+	}
+	t.mu.Unlock()
+
 	entries, err := sftpClient.ReadDir(cwd)
 	if err != nil {
 		return
@@ -209,6 +239,7 @@ func (t *SFTPBrowserTab) refreshRemote() {
 	})
 
 	t.mu.Lock()
+	p.dirCache[cwd] = entries
 	p.entries = entries
 	if p.selIdx >= len(entries) {
 		p.selIdx = 0
@@ -329,6 +360,14 @@ func (t *SFTPBrowserTab) Update(msg tea.Msg) (Tab, tea.Cmd) {
 			p.filter = ""
 
 		case "r":
+			// Force refresh: clear cache then re-read
+			t.mu.Lock()
+			if t.active == paneRemote {
+				delete(t.right.dirCache, t.right.cwd)
+			} else {
+				delete(t.left.dirCache, t.left.cwd)
+			}
+			t.mu.Unlock()
 			if t.active == paneRemote {
 				go t.refreshRemote()
 			} else {