Replace overview agent flow image

[version-1]

Replace Overview Agent Flow Image

Summary

Replace the previous task queue SVG in the README and docs-site Overview pages with the new agent issue flow PNG.

主な変更点:

• Added docs/site/static/img/agent-issue-flow.png.
• Updated README.md and README.ja.md to use the new image.
• Updated English and Japanese docs-site Overview pages to use the new image.

チケットへのリンク

ここはまだない

やったこと

• Copied the generated PNG into the docs-site static image directory.
• Replaced the old agent-task-queue.svg references in README and docs-site Overview content.

動作確認

• npm run build from docs/site
• Confirmed branch is based on latest origin/main
• Confirmed working tree is clean before PR creation

レビュー & 動作確認 チェックリスト

• README image - README and README.ja.md render the new PNG.
• Docs overview image - English and Japanese docs-site Overview pages render the new PNG.
• Asset path - docs/site/static/img/agent-issue-flow.png is committed and referenced correctly.

推奨テスト計画:

1. Run npm run build from docs/site.
2. Open README preview and docs-site Overview pages.
3. Confirm the new image renders in English and Japanese surfaces.

その他気になることや相談ごと

なし

Notes
Requested by: user