test(host_agent): agent config parser unit tests

Add read_config/ConfigError unit tests covering flat key-value parsing,
blank lines/comments, list fields, defaults, missing required keys, and
malformed lines. Also add tests/__init__.py to fix pytest namespace
collision with tests/plugins/ shadowing the root plugins/ package.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/plugins/host_agent/test_agent_config.py

@@ -0,0 +1,60 @@
+# tests/plugins/host_agent/test_agent_config.py
+"""Unit tests for the agent's homegrown config parser."""
+import pytest
+from plugins.host_agent.agent import read_config, ConfigError
+
+
+def test_parses_flat_key_value(tmp_path):
+    p = tmp_path / "agent.conf"
+    p.write_text(
+        "url = https://roundtable.example\n"
+        "token = abc123\n"
+        "interval_seconds = 45\n"
+    )
+    cfg = read_config(str(p))
+    assert cfg["url"] == "https://roundtable.example"
+    assert cfg["token"] == "abc123"
+    assert cfg["interval_seconds"] == 45
+
+
+def test_ignores_blank_lines_and_comments(tmp_path):
+    p = tmp_path / "agent.conf"
+    p.write_text(
+        "# top comment\n"
+        "\n"
+        "url = https://x\n"
+        "  # indented comment\n"
+        "token = t\n"
+    )
+    cfg = read_config(str(p))
+    # interval_seconds defaults to 30 when unset
+    assert cfg["url"] == "https://x"
+    assert cfg["token"] == "t"
+
+
+def test_parses_mounts_as_list(tmp_path):
+    p = tmp_path / "agent.conf"
+    p.write_text("url = x\ntoken = y\nmounts = /, /mnt/data, /srv\n")
+    cfg = read_config(str(p))
+    assert cfg["mounts"] == ["/", "/mnt/data", "/srv"]
+
+
+def test_missing_required_fields_raises(tmp_path):
+    p = tmp_path / "agent.conf"
+    p.write_text("url = https://x\n")
+    with pytest.raises(ConfigError, match="token"):
+        read_config(str(p))
+
+
+def test_malformed_line_raises(tmp_path):
+    p = tmp_path / "agent.conf"
+    p.write_text("url https://x\ntoken = y\n")
+    with pytest.raises(ConfigError):
+        read_config(str(p))
+
+
+def test_default_interval_seconds(tmp_path):
+    p = tmp_path / "agent.conf"
+    p.write_text("url = x\ntoken = y\n")
+    cfg = read_config(str(p))
+    assert cfg["interval_seconds"] == 30