feat(dsh): adapt to DSH 0.1.5-alpha.1

Move the plugin onto the DSH 0.1.5-alpha.1 baseline (peer floor
^0.1.5-alpha.1, CI pinned to the alpha dist-tag) and fix the two host
contract changes that alpha line introduced.

Baseline:
- all @deepseek-ai/dsh-* peer/dev deps -> 0.1.5-alpha.1; optional peer
  @deepseek-ai/dsh-client-ui-sidebar-right (declared, unused until the
  native-surface phase); devDep @deepseek-ai/dsh-agent-loop (inbox fold)
- dsh.plugin.json engines >=0.1.5-alpha.1; version 0.19.0-alpha.0;
  SIDEBAR_SERVICE_VERSION follows

Live assistant stream (assistant/chunk is gone):
- 0.1.5 publishes in-flight model deltas as process-local
  agent/assistant-stream frames instead of durable assistant/chunk events
  and embeds the settled stream in assistant/message / assistant/attempt.
  src/assistant-live.ts folds the frames into a bounded per-session buffer;
  sidechat.events serves the current attempt as `live` rows (replaced every
  poll, never a delta) and the transcript renders them; the inherited
  in-progress snapshot reads message content / attempt stream / live frames.

Cold session reads (persistence.inspect is gone):
- 0.1.5 reads a stored session through an explicit read handle
  (open(id,'read') -> handle.read() -> close()). src/session-store.ts owns
  that protocol; every cold read (sidechat transcript, cold-resume preset,
  session.cwd, changes replay) goes through it.

Dead code and docs:
- drop the remote.session.openWorkspacePath interception: 0.1.5's chat opens
  files through ctx.sidebarRight.openResource instead, so the wrapper had no
  caller and would hijack the host's "open in app" gesture; the
  interceptOpenPath pref, its settings row and its locale keys go with it
- AGENTS.md §3 + external-plugin-guide.md describe the new baseline
- vitest setup bridges Node's localStorage accessor to jsdom's store (the
  pre-existing 26 failures on Node >= 22)
- desktop-layout e2e seeds through host RPC and types into the Lexical
  composer (0.1.5 replaced the textarea) instead of driving the directory
  picker

Verified: pnpm typecheck / lint / build / test (124 files, 1327 tests) /
check:consumer-types, plus pnpm test:mount against a real
@deepseek-ai/dsh@0.1.5-alpha.1 host (18/18).

src/client/locales-vi.ts

@@ -237,8 +237,6 @@ export const vi: Record<string, string> = {
   settingsWidthTitle: 'Tỷ lệ chiều rộng mặc định',
   settingsWidthDesc: 'Tỷ lệ phần trăm chiều rộng cửa sổ mà thẻ bên chiếm cho phiên mới (20–60)',
   settingsWidthSuffix: '%',
-  settingsOpenPathTitle: 'Mở tệp chat trong thanh bên',
-  settingsOpenPathDesc: 'Khi nhấp link tệp trong chat (dòng công cụ, danh sách sản phẩm, nhắc tệp), mở trong trình soạn thảo thanh bên thay vì ứng dụng mặc định hệ thống',
   settingsOpenToolsTitle: 'Tiêm công cụ mở thanh bên cho mô hình',
   settingsOpenToolsDesc: 'Khi bật, mô hình có thể mở tệp, thư mục và trang HTTP(S) trong thanh bên qua công cụ sidebar_open (mặc định tắt)',
   settingsTitleBarTitle: 'Chế độ tương thích thanh tiêu đề',