refactor(office): Office 技能统一读取包内 assets，移除包外 office-skills 拷贝与 DSH_BUNDLED_OFFICE_SKILLS

- web-app、sdk-app 的 skill-office 不再覆盖 assetRoot；pythonEnvironment 不变
- Desktop 与 Python SDK 打包不再生成 office-skills 资源目录，删除 prepareOfficeSkillAssets 与 skillSource
- Desktop 打包 smoke 校验 4 个 Office 技能可从运行时归档列出并加载
- 同步测试、README、Agent Note，新增升级指南 office-skill-resources

python/sdk/tests/test_release_version.py

@@ -150,9 +150,9 @@ def test_stage_runtime_copies_platform_payload(
     office_asset.parent.mkdir(parents=True)
     office_asset.write_bytes(b"office data")
     resources = executable.with_name(executable.name.removeprefix("deepseek-harness-sdk-runtime-").removesuffix(".exe"))
-    resource = resources / "office-skills/office-docx/SKILL.md"
+    resource = resources / "downloads.json"
     resource.parent.mkdir(parents=True)
-    resource.write_text("# Word documents\n")
+    resource.write_text("{}\n")
     destination = tmp_path / "staging"
 
     build_python_release.stage_runtime(destination, "1.2.3", executable, executable.name)
@@ -164,7 +164,7 @@ def test_stage_runtime_copies_platform_payload(
         if path.is_file()
     } == expected
     assert not (runtime_dir / office.name).exists()
-    assert (runtime_dir / resources.name / resource.relative_to(resources)).read_text() == "# Word documents\n"
+    assert (runtime_dir / resources.name / resource.relative_to(resources)).read_text() == "{}\n"
     pyproject = (destination / "pyproject.toml").read_text()
     assert 'license = "MIT"' in pyproject
     assert 'license-files = ["LICENSE", "THIRD_PARTY_NOTICES.md"]' in pyproject