fix(setup): auto-install matrix-nio during hermes setup (#3873)

Setup previously only printed a manual install hint for matrix-nio,
causing the gateway to crash with 'matrix-nio not installed' after
configuring Matrix. Now auto-installs matrix-nio (or matrix-nio[e2e]
when E2EE is enabled) using the same uv-first/pip-fallback pattern
as Daytona and Modal backends.

Also adds hermes-agent[matrix] to the [all] extra in pyproject.toml
and a regression test to keep it there.

Co-authored-by: Gutslabs <Gutslabs@users.noreply.github.com>
Co-authored-by: cutepawss <cutepawss@users.noreply.github.com>

tests/test_project_metadata.py

@@ -0,0 +1,18 @@
+"""Regression tests for packaging metadata in pyproject.toml."""
+
+from pathlib import Path
+import tomllib
+
+
+def _load_optional_dependencies():
+    pyproject_path = Path(__file__).resolve().parents[1] / "pyproject.toml"
+    with pyproject_path.open("rb") as handle:
+        project = tomllib.load(handle)["project"]
+    return project["optional-dependencies"]
+
+
+def test_all_extra_includes_matrix_dependency():
+    optional_dependencies = _load_optional_dependencies()
+
+    assert "matrix" in optional_dependencies
+    assert "hermes-agent[matrix]" in optional_dependencies["all"]