docs(plugin): refocus the certification page on developer decisions

Rewrite plugin/certified-plugins in all three locales around the
questions a plugin developer actually asks, and make it the single home
for certification: what it is, why it exists, when it is needed, what
changes after approval, and what the contract requires.

- Decision framing restored, including a needs/does-not-need table and
  the explicit statement that most plugins do not need certification.
- Full manifest example, accepted values for both declaration fields and
  the SDK version that recognises them.
- Constraints kept and tightened: stateless rules, allowed/forbidden
  table, anti-patterns with correct/incorrect snippets, Runner notes,
  self-check list.
- Submission flow moved onto this page so it no longer depends on the
  publishing page.
- Operator content that duplicates the Core architecture document
  removed (Cloud admission matrix, OSS issuer keys, certificate fields,
  internal review tiers).

publish/market is now publishing-only with a one-line pointer, and its
misplaced plugin_submission screenshot moves back under the upload
section where it belongs. dev/basic-info replaces the commented-out
manifest fields with a link to the contract page.

ja had been missing whole sections (36 lines); all three locales now
share the same section structure.

ja/plugin/dev/basic-info.mdx

@@ -28,11 +28,10 @@ execution:
   python:
     path: main.py  # 変更しないでください
     attr: HelloPlugin  # 変更しないでください
-  # ステートレス単一インスタンス規約へ移行し、認証を申請する場合のみ追加：
-  # sharedRuntime: shared-runtime-v1
-  # componentModel: stateless-v1
 ```
 
+認証を申請し、複数のインストールで 1 つのランタイムを共有する場合は、`execution` 配下に `sharedRuntime` と `componentModel` も宣言します。詳細は[認証プラグインと共有実行](/ja/plugin/certified-plugins)を参照してください。
+
 プラグインの多言語サポートは[RFC 4646](https://datatracker.ietf.org/doc/html/rfc4646)標準に従います。現在サポートされている言語は次のとおりです:
 
 - `en_US` 英語（必須）