feat(skill): unify skill activation as authorized tools

Expose skill tools (activate/register_skill/native exec) like native tools
instead of gating them behind the skill_authoring capability:
- toolmgr.get_all_tools drops include_skill_authoring; SkillToolLoader
  self-gates on sandbox + skill_mgr
- preproc drops the include_skill_authoring branch; pipeline-bound skills
  and the skills resource gate on skill_mgr presence

Persist activated skills into host.activated_skills conversation state so
they survive across runs (host writes at activate; last-write-wins); drop
the dead restore_activated_skills helper.

Prefill ToolResource.parameters host-side (tool_mgr.get_tool_schema) so
runners build LLM tools without per-tool get_tool_detail round-trips.

Align agent-runner-pluginization design docs to the all-tool model.

tests/unit_tests/agent/test_resource_builder.py

@@ -97,6 +97,9 @@ def app():
     mock_app.model_mgr = Mock()
     mock_app.rag_mgr = Mock()
     mock_app.rag_mgr.get_knowledge_base_by_uuid = AsyncMock(return_value=None)
+    mock_app.skill_mgr = None
+    mock_app.tool_mgr = Mock()
+    mock_app.tool_mgr.get_tool_schema = AsyncMock(return_value=(None, None))
     return mock_app
 
 
@@ -278,7 +281,16 @@ async def test_build_models_deduplicates_query_and_config_models(app):
 
 @pytest.mark.asyncio
 async def test_build_tools_authorizes_query_declared_tools(app):
-    """Tools discovered by Pipeline preprocessing become run-scoped authorized resources."""
+    """Tools discovered by Pipeline preprocessing become run-scoped authorized
+    resources, with full parameters schema prefilled by the host."""
+    app.tool_mgr.get_tool_schema = AsyncMock(
+        side_effect=lambda name: {
+            'qa_plugin_echo': (
+                'Echo test tool',
+                {'type': 'object', 'properties': {'text': {'type': 'string'}}},
+            ),
+        }.get(name, (None, None))
+    )
     descriptor = make_descriptor(
         capabilities={'tool_calling': True},
     )
@@ -296,14 +308,16 @@ async def test_build_tools_authorizes_query_declared_tools(app):
         {
             'tool_name': 'qa_plugin_echo',
             'tool_type': None,
-            'description': None,
+            'description': 'Echo test tool',
             'operations': ['detail', 'call'],
+            'parameters': {'type': 'object', 'properties': {'text': {'type': 'string'}}},
         },
         {
             'tool_name': 'qa_mcp_echo',
             'tool_type': None,
             'description': None,
             'operations': ['detail', 'call'],
+            'parameters': None,
         },
     ]