docs: attach PR screenshots with GitHub CLI

[Lampese]

Related issue

Same-repository documentation follow-up; no intake issue.

Problem / pressure

The screenshot recommendation in #1744 does not show how to upload images, and its wording mentions committing captures. Agents need a concrete way to share before/after screenshots without adding review-only image files to Git history.

Summary

Point authors to GitHub CLI's native gh pr create --attach and gh pr edit --attach support. Keep PR-only screenshots in temporary or ignored paths, out of commits. The visual guide includes a copyable command that uploads a before/after pair and rewrites local image references in the complete PR body to GitHub attachment URLs.

Preserve screenshot optionality, privacy inspection, existing template headings and the absence of an automated screenshot gate. Update the owning bilingual process note.

Visual explanation

Simple change: documentation clarifies the existing screenshot workflow; the command example is the useful review artifact.

Sanitized captures in temporary/ignored paths
  -> gh pr edit --attach + complete body file
  -> GitHub attachment URLs in the Before / After table

Before / after

Before	After
Privacy guidance mentions uploading or committing screenshots	PR-only captures stay outside Git commits and are uploaded as attachments
Generic advice to provide accessible artifacts	Concrete --attach command and local Markdown-reference rewriting guidance
Optional before/after comparisons	Same optional recommendation, with no omission explanation required

Test plan

• node --test .github/scripts/check-pr-template.test.mjs .github/scripts/pr-policy.test.mjs: 23 tests passed.
• Installed gh pr create --help and gh pr edit --help: verified native attachment flags, body-file behavior and reference rewriting.
• pnpm format: passed.
• pnpm run docs status: reviewed.
• pnpm run docs check: six existing missing Kimi/Pi submodule links; no new errors or protected-topic changes.
• Full type/build/runtime checks were not rerun for this documentation-only change.

Context handoff

Internal same-repository branch. The owning bilingual process note records the attachment clarification alongside the existing optional screenshot recommendation.