feat: adapt to DSH 0.1.2-alpha.1 (Remote gateway + token auth + MarkdownText labels)

Dual-version compatibility: the plugin now works identically on
0.1.0-rc.8 ~ 0.1.1-rc.2 and 0.1.2-alpha.1 (the latter verified against a
source build of the dsh-v0.1.2-alpha.1 tag: mount smoke 14/14 + aggregate
double-mount; 0.1.1-rc.2 re-verified 14/14).

- MarkdownText: alpha.1 renamed the flat optional `codeLabels` prop to a
  required nested `labels: { code: {copyLabel, copiedLabel}, footnotes }`;
  the old prop alone crashes fence rendering with "reading 'code'". All
  four render sites (mermaid / MarkdownHtml / TextEditor / SideChatView)
  now go through src/client/markdown-labels.tsx (dual-shape object passed
  under both prop names).
- e2e mount lanes speak both host dialects (tests/e2e/host-protocol.ts +
  host.ts, unit-locked by tests/e2e-host-protocol.spec.ts):
  - one-time-token browser auth: the launch URL grep extends past the
    `/?token=` query (truncating at `/` loses the token), goto navigates
    the token URL (browser cookie exchange), and stamped navigations
    pre-seed the context cookie via addCookies — the exchange 303 drops
    sibling query params;
  - Remote gateway: dot endpoints first, slash endpoints on 404 fallback,
    with args keyed by the controller parameter name (workspace/create ->
    {request}, session/list -> {_request}; verified on a live host).
- package.json: drop the @deepseek-ai/dsh-client-runtime peer (package
  removed upstream in alpha.1; zero references in the source — the chunk
  externals entry stays and is resolution-tolerant).
- scripts/e2e-mount.sh: fix a latent set -u crash in the npx fallback
  branch ($DSH_CMD followed by a full-width comma parsed as part of the
  variable name).
- CI pin stays at @deepseek-ai/dsh@0.1.1-rc.2 until alpha.1 publishes to
  npm (comment updated); README/AGENTS document the new contracts.
- Version lockstep bumped to 0.17.1.

dsh.plugin.json

@@ -1,6 +1,6 @@
 {
   "id": "dsh-external/dsh-better-sidebar",
-  "version": "0.17.0",
+  "version": "0.17.1",
   "main": "./lib/index.js",
   "description": "VSCode 风格右侧侧边栏：文件资源管理器 / 编辑器 / 终端 / Git / 浏览器，按会话隔离。暴露服务供其他插件注册侧边栏页面和文件预览器",
   "engines": {