feat: native SSH delegation via tea.ExecProcess + Gruvbox palette

Phase A — Tamagosh-inspired redesign:
- Replace goroutine-based SSH (crypto/ssh) with tea.ExecProcess + native ssh binary
- Zero-lag SSH: native binary pegang TTY langsung, ga ada Go buffering
- Password auth via sshpass -e (SSHPASS env)
- Key auth via ssh -i <tmpfile> + SSH_ASKPASS for passphrase
- ControlMaster sockets for fast reconnect
- Add askpass subcommand for SSH_ASKPASS support
- Gruvbox Material Dark Hard palette for comfortable viewing
- Clean up old session messages (openSessionMsg, sessionOutputMsg, sessionDoneMsg)
- Remove 354-line session.go, replace with 150-line ssh.go

pkg/tui/tabs.go

@@ -196,6 +196,6 @@ func renderTabBar(tm *TabManager) string {
 
 // renderStatusBar renders the bottom status bar
 func renderStatusBar(tm *TabManager) string {
-	hints := "Ctrl+Tab:switch  Ctrl+Q:close  ↑↓:nav  Enter:select  Ctrl+N:add  Ctrl+F:SFTP  Ctrl+K:keys  Ctrl+P:snippets  q:quit"
+	hints := "Ctrl+Tab:switch  Ctrl+Q:close  ↑↓:nav  Enter:SSH  Ctrl+N:add  Ctrl+F:SFTP  Ctrl+K:keys  Ctrl+P:snippets  q:quit"
 	return StatusBarStyle.Render(hints)
 }