docs(readme): remove security warning banners and fix table formatting

Remove ohmyopencode.com impersonation warnings from all localized READMEs
and fix markdown table column alignment across ja, ko, ru, zh-cn variants.
Also remove Sisyphus Labs note block from ko README.

🤖 Generated with assistance of [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

README.md

@@ -1,14 +1,3 @@
-> [!WARNING]
-> **Security warning: impersonation site**
->
-> **ohmyopencode.com is NOT affiliated with this project.** We do not operate or endorse that site.
->
-> OhMyOpenCode is **free and open-source**. Do **not** download installers or enter payment details on third-party sites that claim to be "official."
->
-> Because the impersonation site is behind a paywall, we **cannot verify what it distributes**. Treat any downloads from it as **potentially unsafe**.
->
-> ✅ Official downloads: https://github.com/code-yeongyu/oh-my-opencode/releases
-
 > [!NOTE]
 >
 > [![Sisyphus Labs - Sisyphus is the agent that codes like your team.](./.github/assets/sisyphuslabs.png?v=2)](https://sisyphuslabs.ai)