fix: use script command for PTY instead of modifying SSHService

- Revert SSHService exec() back to original (remove PTY parameter)
- AgentService now writes installer to /tmp/ first, then runs via
  script -q -c to create a PTY for sudo (handles requiretty)
- Falls back to direct sudo bash if script is unavailable
- Cleans up temp files after execution
- Added mkdir -p for /usr/local/bin in installer
- Added file verification and byte-count after writing agent binary

install/agent-install.sh

@@ -21,6 +21,7 @@ echo "[1/5] Creating config directory..."
 mkdir -p "$CONFIG_DIR"
 
 echo "[2/5] Installing agent binary..."
+mkdir -p "$(dirname "$AGENT_BIN")"
 cat > "$AGENT_BIN" << 'AGENTSCRIPT'
 #!/bin/bash
 set -e
@@ -49,7 +50,6 @@ collect_metrics() {
 }
 
 push_metrics() {
-    local payload
     payload=$(cat <<EOF
 {
     "agent_key": "$AGENT_KEY",
@@ -75,7 +75,7 @@ main() {
         exit 1
     fi
     echo "ServerManager Agent started (interval: ${INTERVAL}s)"
-    sleep 5
+    sleep 2
     while true; do
         collect_metrics
         http_code=$(push_metrics)
@@ -91,6 +91,12 @@ main
 AGENTSCRIPT
 chmod +x "$AGENT_BIN"
 
+if [ ! -f "$AGENT_BIN" ]; then
+    echo "ERROR: Agent binary was not created at $AGENT_BIN"
+    exit 1
+fi
+echo "  Verified: $AGENT_BIN ($(wc -c < "$AGENT_BIN") bytes)"
+
 echo "[3/5] Writing config..."
 cat > "$CONFIG_FILE" << EOF
 SERVER_URL="$SERVER_URL"