feat(plugins validate): fail trees with nothing to load; check dependency declarations

A plugin.yaml with no __init__.py, desktop/plugin.js or plugin.json beside it
installs "successfully" and does nothing (pip-layout repos whose code sits under
src/ behind an entry point). The validator and catalog CI now fail that shape
and check declared Python dependencies parse and are index specs; direct-URL
requirements warn.

Tests: conflicting candidate refused with peers untouched; post-update re-apply
drops only the culprit and keeps the memory provider. Loader wording test
updated to the new hint.

hermes_cli/plugin_validate.py

@@ -508,12 +508,62 @@ def validate_plugin_dir(plugin_dir: Path) -> ValidationReport:
     _check_requires_hermes(report, manifest)
     _check_config_spec(report, manifest)
     _check_requires_env(report, manifest)
+    _check_loadable(report, plugin_dir)
+    _check_python_dependencies(report, plugin_dir)
     recorded = _check_capabilities(report, manifest, plugin_dir)
     _check_builtin_collisions(report, manifest, recorded)
     _check_security_scan(report, plugin_dir)
     return report
 
 
+_LOADABLE_ENTRYPOINTS = ("__init__.py", "desktop/plugin.js", "plugin.json")
+
+
+def _check_loadable(report: ValidationReport, plugin_dir: Path) -> None:
+    """A plugin.yaml with nothing beside it that Hermes can load (no ``register()`` module, no
+    desktop bundle, no portable manifest) installs "successfully" and does nothing — a pip-layout
+    repo whose code lives under ``src/`` behind an entry point is the usual shape."""
+    present = [rel for rel in _LOADABLE_ENTRYPOINTS if (plugin_dir / rel).is_file()]
+    report.add(
+        "loadable", bool(present),
+        f"entry: {', '.join(present)}" if present else
+        "nothing to load: no __init__.py, desktop/plugin.js or plugin.json beside plugin.yaml "
+        "(pip-layout packages need a directory-plugin wrapper with a pyproject.toml declaring the deps)",
+    )
+
+
+def _check_python_dependencies(report: ValidationReport, plugin_dir: Path) -> None:
+    """Declared deps (pyproject ``[project].dependencies`` or manifest ``python_dependencies``) must be
+    well-formed PEP 508 specs the installer will accept; a plugin opting out with
+    ``python_runtime: external`` declares none."""
+    from hermes_cli.plugin_python_deps import read_declaration
+
+    try:
+        decl = read_declaration(plugin_dir)
+    except Exception as exc:
+        report.add("python dependencies", False, f"declaration invalid: {exc}")
+        return
+    if decl.external:
+        report.add("python dependencies", True, "external runtime (plugin manages its own)")
+        return
+    from hermes_cli.plugin_python_deps import applicable_specs, unsupported_specs
+
+    urls = unsupported_specs(decl.specs)
+    if urls:
+        report.warn("python dependencies: direct URL requirement(s) are never auto-installed, users must "
+                    f"install them by hand: {', '.join(urls)}")
+    installable = applicable_specs(decl.specs)
+    rejected = [s for s in installable if not _spec_is_safe(s)]
+    detail = f"{len(installable)} installable from {decl.source}" if decl.source else "none declared"
+    report.add("python dependencies", not rejected,
+               f"unsafe spec(s): {', '.join(rejected)}" if rejected else detail)
+
+
+def _spec_is_safe(spec: str) -> bool:
+    from tools.lazy_deps import _spec_is_safe as safe
+    return safe(spec)
+
+
 def _check_security_scan(report: ValidationReport, plugin_dir: Path) -> None:
     """Run the install-time scanner at admission, so a pin a reviewer approves is one the
     installer will accept: ``dangerous`` fails the entry; ``caution`` findings surface as

tests/hermes_cli/test_plugin_manifest_v2.py

@@ -366,7 +366,7 @@ class TestPythonDependenciesSeam:
         assert mgr._plugins["pipful"].enabled
         assert "definitely-not-a-real-package-64165" in caplog.text
         assert "pip install" in caplog.text
-        assert "does not install plugin dependencies automatically" in caplog.text
+        assert "hermes plugins enable pipful" in caplog.text
         assert calls == []
 
     def test_satisfied_pip_dep_is_quiet(self, hermes_home, caplog):

tests/hermes_cli/test_plugin_python_deps.py

@@ -53,32 +53,33 @@ def test_conflicting_candidate_is_refused_and_enabled_plugins_are_untouched(tmp_
     resolve, calls = _fake_resolver({"tabulate<0.9"})
     monkeypatch.setattr(deps, "resolve", resolve)
     monkeypatch.setattr(deps, "core_constraints", lambda root: ["httpx==0.28.1"])
-    monkeypatch.setattr(deps, "all_homes", lambda: [home])
+    monkeypatch.setattr(deps, "dependency_homes", lambda: [home])
 
     with pytest.raises(deps.DependencyConflict):
         deps.check_candidate(deps.read_declaration(candidate), home=home, project_root=tmp_path)
 
     # The dry run saw the union (candidate + enabled peer) and never ran a real install.
-    assert calls == [["tabulate<0.9", "tabulate>=0.9"]]
+    assert [sorted(c) for c in calls] == [["tabulate<0.9", "tabulate>=0.9"]]
     assert (home / "plugins" / "good").is_dir()
     assert "good" in (home / "config.yaml").read_text()
 
 
 def test_reapply_disables_non_memory_plugin_loudly_and_keeps_memory_provider(tmp_path, monkeypatch):
-    home = _home(tmp_path, ["memory", "weather", "sidecar"])
+    home = _home(tmp_path, ["memory", "weather", "sidecar", "aaa-innocent"])
     _plugin(home, "memory", '"mnemosyne-memory>=3"', memory=True)
     _plugin(home, "weather", '"httpx<0.20"')
     _plugin(home, "sidecar", '"torch==99"', external=True)
+    _plugin(home, "aaa-innocent", '"tabulate>=0.9"')  # sorts before the culprit; must NOT be sacrificed
     resolve, calls = _fake_resolver({"httpx<0.20"})
     monkeypatch.setattr(deps, "resolve", resolve)
     monkeypatch.setattr(deps, "core_constraints", lambda root: ["httpx==0.28.1"])
-    monkeypatch.setattr(deps, "all_homes", lambda: [home])
+    monkeypatch.setattr(deps, "dependency_homes", lambda: [home])
     disabled: list[tuple[Path, str]] = []
 
     report = deps.reapply_all(project_root=tmp_path, disable=lambda h, n: disabled.append((h, n)))
 
     assert disabled == [(home, "weather")]
     assert report.dropped and report.dropped[0][0] == "weather"
-    assert report.installed == ["mnemosyne-memory>=3"]
+    assert sorted(report.installed) == ["mnemosyne-memory>=3", "tabulate>=0.9"]
     # External-runtime plugin never joined the union; memory provider was the survivor.
     assert all("torch==99" not in c for c in calls)

tests/hermes_cli/test_plugins_cmd_catalog.py

@@ -76,7 +76,8 @@ def test_catalog_name_installs_pinned_sha_with_sidecar_then_update_repins(world,
 
     # Dashboard update on a catalog install = re-pin. Pin unchanged → no-op.
     assert pc.dashboard_update_user_plugin("cat-plugin") == {
-        "ok": True, "name": "cat-plugin", "sha": world["sha1"], "unchanged": True}
+        "ok": True, "name": "cat-plugin", "sha": world["sha1"], "unchanged": True,
+        "python_dependencies": [], "warnings": []}
     # Bump the catalog pin → the checkout moves to exactly that sha.
     world["state"]["pin"] = world["sha2"]
     assert pc.dashboard_update_user_plugin("cat-plugin")["unchanged"] is False