docs: add Simplified Chinese onboarding and search

[rmcdaniel]

Advances #169 with Simplified Chinese (zh-Hans).

Changes

• Translate all eleven onboarding/core guides: deployment choice, installation,
  complete PHP/Python/Rust quickstart, embedded authoring, core concepts,
  determinism, idempotency and recovery. Translate home, navigation, search and
  sidebar descriptions. Review terminology and technical meaning against English.
• Preserve executable examples, API identifiers, shared artifact values and
  English heading anchors. Extend the existing example/source-review check and
  README upkeep guidance to Chinese. Reference and 1.x pages retain explicit
  English notices and direct English links.
• Select the existing plugin's Jieba Chinese segmentation for this locale.
  Reset its cached index-builder configuration when the language set changes,
  since Docusaurus builds all locales in the same process. A focused regression
  reproduces the unpatched English-to-Chinese failure and checks the fixed
  English → Chinese → English sequence, Chinese partial-word search, Ukrainian
  text, English API terms and serialized-index reloads.
• Correct the shared how-it-works guide's clock helper to the current v2
  Workflow::now() on Workflow\V2\Workflow in all five languages.

Verification

Code blocks match English across eleven Spanish, eleven Portuguese and eleven
Chinese guides. The focused search regression and full five-locale Node 24 build
pass. All four source gates pass on 6c4be18f58eb03afa464e1295e93460743675cdc,
including documentation qualification.

Chromium desktop/mobile checks pass for all eleven Chinese guides, five-locale
metadata, PHP/Python/Rust complete programs, rendered artifact values, relative
links, English reference/1.x notices, stable anchors, home and language switching.
Chinese 恢复, 幂等, 工作流 and English activity search pass. English,
Ukrainian скасування, Spanish recuperación and Portuguese recuperação
search remain usable. Representative home/mobile layouts were visually checked.

Merged as 8474b426524433dfd45730491e418ef632aa1373, with the tested tree
unchanged. All five main gates and Pages publication
pass. The same full desktop/mobile checks pass against durable-workflow.com at
03:34 UTC. The clean worktree, dependencies, local server and local/remote merged
branch are removed, with GitHub absence verified.

Japanese follows as a separate increment in #169. No package version or runtime
behavior changes.