feat(agent): add [debug] dump_dir config field

agent/test/fixtures/agent.toml

@@ -6,3 +6,6 @@ host_id = "pve-test-01"
 fast_seconds = 15
 medium_seconds = 120
 slow_seconds = 600
+
+[debug]
+dump_dir = "/tmp/proxmox-monitor-test"

agent/test/proxmox_agent/config_test.exs

@@ -14,6 +14,43 @@ defmodule ProxmoxAgent.ConfigTest do
       assert cfg.fast_seconds == 15
       assert cfg.medium_seconds == 120
       assert cfg.slow_seconds == 600
+      assert cfg.dump_dir == "/tmp/proxmox-monitor-test"
+    end
+
+    test "parses [debug] dump_dir when present" do
+      assert {:ok, cfg} = Config.load(@fixture)
+      assert cfg.dump_dir == "/tmp/proxmox-monitor-test"
+    end
+
+    test "dump_dir is nil when [debug] is absent" do
+      tmp = Path.join(System.tmp_dir!(), "agent_nodebug.toml")
+
+      File.write!(tmp, """
+      server_url = "wss://x/socket/websocket"
+      token = "t"
+      """)
+
+      on_exit(fn -> File.rm(tmp) end)
+
+      assert {:ok, cfg} = Config.load(tmp)
+      assert cfg.dump_dir == nil
+    end
+
+    test "dump_dir is nil when set to empty string" do
+      tmp = Path.join(System.tmp_dir!(), "agent_emptydebug.toml")
+
+      File.write!(tmp, """
+      server_url = "wss://x/socket/websocket"
+      token = "t"
+
+      [debug]
+      dump_dir = ""
+      """)
+
+      on_exit(fn -> File.rm(tmp) end)
+
+      assert {:ok, cfg} = Config.load(tmp)
+      assert cfg.dump_dir == nil
     end
 
     test "returns error for missing file" do