Keep sshd_config.d drop-ins working and resolve sftp-server per distro

The wholesale sshd_config replacement is intentional, but two side effects
were not:

- The template had no Include line, so reinstalling dropped the
  `Include /etc/ssh/sshd_config.d/*.conf` that update_ssh_banners_config
  appends, leaving the per-user banner drop-in on disk but inert. Add it as
  the last line: OpenSSH uses the first value it obtains for a keyword, so
  the template's own settings still take precedence over any drop-in and
  only the Match blocks become effective.
- The template hardcoded the Debian path for sftp-server. sshd -t does not
  verify that the binary exists, so SFTP broke silently on distributions
  that ship it elsewhere. install.sh now probes the common locations and
  rewrites the Subsystem line.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

install.sh

@@ -99,6 +99,27 @@ cp "$SSHD_CONFIG" "$BACKUP"
 cp "$SCRIPT_DIR/ssh" "$SSHD_CONFIG"
 chmod 600 "$SSHD_CONFIG"
 
+# The template carries the Debian path for sftp-server. sshd -t does not check
+# that the binary exists, so on other distributions SFTP would silently break.
+SFTP_SERVER=""
+for candidate in \
+    /usr/lib/openssh/sftp-server \
+    /usr/libexec/openssh/sftp-server \
+    /usr/lib/ssh/sftp-server \
+    /usr/libexec/sftp-server
+do
+    if [[ -x "$candidate" ]]; then
+        SFTP_SERVER="$candidate"
+        break
+    fi
+done
+if [[ -n "$SFTP_SERVER" ]]; then
+    sed -i "s|^Subsystem sftp .*|Subsystem sftp $SFTP_SERVER|" "$SSHD_CONFIG"
+    echo "Using sftp-server: $SFTP_SERVER"
+else
+    echo "WARNING: no sftp-server binary found; leaving the Subsystem line unchanged."
+fi
+
 # Validate SSH config (silent)
 if ! sshd -t 2>/dev/null; then
     echo "ERROR: SSH configuration is invalid!"

ssh

@@ -28,3 +28,8 @@ AcceptEnv LANG LC_*
 Subsystem sftp /usr/lib/openssh/sftp-server 
 UsePAM yes
 Banner /etc/bannerssh
+
+# Kept last on purpose. OpenSSH uses the first value it obtains for a keyword,
+# so everything above still wins over any drop-in; this only lets the Match
+# blocks that menu.sh writes to sshd_config.d (per-user banners) take effect.
+Include /etc/ssh/sshd_config.d/*.conf