fix: SFTP stacked mode — render only active pane + indicator bar

Stacked mode (<50 cols) now shows only the active pane (Local/Remote)
with a visual indicator bar. Tab switches between panes. Side-by-side
mode (>=50 cols) unchanged.

CHANGELOG.md

@@ -27,6 +27,12 @@
 - Fixed: key_list_tab & snippet_list_tab were dropping last data row (off-by-one in `rows[:len(rows)-1]`)
 - Fixed: SFTP pane width — lipgloss `Width(n)` renders `n+2` chars (border extra). halfW now `t.width/2-2` to compensate. File names truncate to `…` within inner text area. Filter line also truncated.
 - Verified: zero overflow at 80, 60, 50 (side-by-side), 40, 30 cols (stacked)
+
+### SFTP Stacked Mode Fix (Done)
+- Stacked mode (<50 cols) now renders only the active pane (Local or Remote)
+- Added pane indicator bar: `[Local]  Remote` with active pane highlighted
+- Side-by-side mode (≥50 cols) unchanged — both panes remain visible
+- Tab key now visually switches between panes on narrow terminals
 - Breakpoints: compact (<60), medium (60–100), wide (≥100)
 
 ## v1.0.0 (2025-01-30)