fix(i18n/ja): fix quality issues in 19 Japanese translation files

[lin-bot23]

Summary

Fixes quality issues in 19 Japanese (ja/) translation files based on AI quality review. Each fix is in its own commit.

Changes

Terminology fixes

• Account: login.mdx, create-account.mdx — fixed "API ノード → パートナーノード", "サインイン → ログイン"
• Partner Nodes: luma-text-to-image.mdx, luma-image-to-image.mdx, flux-1-kontext.mdx, api-key-integration.mdx, settings/overview.mdx — fixed "API ノード → パートナーノード"
• Custom Nodes: javascript_about_panel_badges.mdx — fixed Chinese "关于 → 情報"
• CLI: getting-started.mdx — fixed title "クイックスタート → はじめに"
• Tutorials: ltx-2.mdx — fixed Chinese "快速入門 → はじめに", "描述 → 説明"
• Cloud: get_started/cloud.mdx — fixed Chinese "类别 → カテゴリ", "自托管 → セルフホスト", "自有 → 自身の", "近日予定 → 近日公開"
• Troubleshooting: model-issues.mdx — fixed Chinese "模型 → モデル"
• Manager: install.mdx — fixed "管理者 → マネージャー"
• Settings: overview.mdx — fixed "拡張機能 → 拡張", "について → 情報"
• Agent Tools: partner-mcp.mdx — fixed "アローリスト → 許可リスト"

Content fixes

• comfy-cli/reference.mdx — restored missing import GenerateCliReference and entire "Generate (partner nodes) — Beta" section
• comfy-cli/getting-started.mdx — restored missing "Call partner nodes directly" section with all subsections, code blocks, Info/Tip/Note blocks; fixed model download command
• partner-mcp.mdx — added missing sign-up link in Warning block, added hyperlink to Comfy API key
• astra-2.mdx — restored missing "the clip feels richer—not only bigger" content; fixed missing "template" reference; fixed "Expand advanced controls" simplification
• cloud/overview.mdx — added missing Standard row in parallel execution table

Frontmatter fixes

• Removed extraneous translationSourceHash and translationFrom fields
• Removed invented comments from description fields (in configuration.mdx, install.mdx, troubleshooting.mdx, astra-2.mdx)
• Added computed reviewSourceHash (first 8 chars of SHA-256 of English source)