docs(plugins): document Runner components and APIs

[RockChinQ]

Documents unified Runner plugin development in Chinese, English, and Japanese. The guide covers both Runner usages: implementing Agent execution and handling declared platform events for plugin processors. It includes component manifests, all 17 supported platform events, streaming replies, debugging, and processor binding.

Reorganizes the plugin API reference around each component's context, then documents platform APIs and LangBot APIs separately. It also adds validation scripts that execute the tutorial examples across all three translations and verify that their Python and YAML stay aligned.

Validation:

• Runner tutorial verification: 10 cases passed with the matching SDK.
• npm test: 36 Node tests and 14 Python tests passed.
• npm run typecheck passed.
• npm run build passed, including all 30 static-output checks.
• Local browser preview checked; the example plugin was exercised through the Host/runtime and a localhost OneBot peer. Third-party platform delivery was not covered by these local checks.