docs: salvage focused stale PR contributions

- add Vite and Redis pattern skills from closed stale PRs

- add frontend-slides support assets

- port skill-comply runner fixes and LLM prompt/provider regressions

- harden agent frontmatter validation and sync catalog counts

tests/test_templates.py

@@ -0,0 +1,71 @@
+import pytest
+
+from llm.prompt import (
+    TEMPLATES,
+    clear_templates,
+    deregister_template,
+    get_template,
+    get_template_or_default,
+    register_template,
+)
+
+
+@pytest.fixture(autouse=True)
+def restore_template_registry():
+    snapshot = dict(TEMPLATES)
+    clear_templates()
+    yield
+    try:
+        clear_templates()
+    finally:
+        TEMPLATES.update(snapshot)
+
+
+@pytest.mark.unit
+def test_register_template_exposes_public_template_mapping():
+    register_template("system", "You are helpful.")
+
+    assert get_template("system") == "You are helpful."
+    assert get_template_or_default("missing", "fallback") == "fallback"
+    assert TEMPLATES["system"] == "You are helpful."
+
+
+@pytest.mark.unit
+def test_templates_mapping_remains_mutable_for_existing_callers():
+    TEMPLATES["legacy"] = "Use the existing public mapping."
+
+    assert get_template("legacy") == "Use the existing public mapping."
+
+
+@pytest.mark.unit
+def test_deregister_template_removes_named_template():
+    register_template("system", "You are helpful.")
+
+    deregister_template("system")
+
+    assert get_template("system") is None
+
+
+@pytest.mark.unit
+def test_clear_templates_removes_all_registered_templates():
+    register_template("system", "You are helpful.")
+    register_template("user", "Answer clearly.")
+
+    clear_templates()
+
+    assert TEMPLATES == {}
+
+
+@pytest.mark.unit
+@pytest.mark.parametrize(
+    ("name", "template", "error_match"),
+    [
+        ("", "content", "Template name must be a non-empty string"),
+        ("   ", "content", "Template name must be a non-empty string"),
+        ("system", "", "Template content must be a non-empty string"),
+        ("system", "   ", "Template content must be a non-empty string"),
+    ],
+)
+def test_register_template_rejects_empty_inputs(name, template, error_match):
+    with pytest.raises(ValueError, match=error_match):
+        register_template(name, template)