docs: add Hidden & Pre-Filled section to User Input page

[RiskeyL]

Summary

• Documents the redesigned hidden field feature shipped in chore: add query generator before lauch webapp dify#35416. Adds a new H2 "Hide and Pre-Fill Input Fields" to the User Input page (en/zh/ja), covering the mental model, security warning, two-step setup, and three delivery contexts (shareable URL, static embed config, dynamic per-visitor embed).
• Adds three macro translation principles to tools/translate/formatting-zh.md (voice it / short verbal clauses / match register) plus a read-aloud check, complementing the existing pattern-based guidance.

[Copilot]

Pull request overview

Adds documentation for the redesigned “Hidden & Pre-Filled” input field capability on the User Input node pages (EN/JA/ZH), and extends the Chinese translation formatting guide with higher-level writing principles.

Changes:

• Added a new “Hidden & Pre-Filled” section to the User Input node docs (en/ja/zh), including setup steps and delivery contexts (shareable link + embed).
• Replaced the previous “hide field” tip with a pointer to the new section.
• Updated tools/translate/formatting-zh.md with macro-level translation principles and a read-aloud check.

Reviewed changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated 3 comments.

File	Description
en/use-dify/nodes/user-input.mdx	Adds the new “Hide and Pre-Fill Input Fields” section and updates the related tip.
ja/use-dify/nodes/user-input.mdx	Japanese version of the new section and updated tip (contains a fragment link issue).
zh/use-dify/nodes/user-input.mdx	Chinese version of the new section, updated terminology, and updated tip (contains fragment link + UI label issues).
tools/translate/formatting-zh.md	Adds higher-level translation principles to improve natural Chinese output.

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