Fix video owner channel link after SPA navigation

[OnlyYu1996]

Summary

• refresh the cached watch-page owner channel elements during video page updates
• restore the current owner link from YouTube renderer endpoint data before applying the default channel tab rewrite
• add a regression test for reused owner link nodes retaining a previous channel URL

Fixes #1485

Tests

• npm ci
• npx jest tests/unit/video-owner-channel-link.test.js --runInBand
• npx jest tests/unit/watch-later-buttons.test.js tests/unit/popup-preview-button.test.js tests/unit/remaining-duration.test.js tests/unit/video-owner-channel-link.test.js --runInBand
• ESLINT_USE_FLAT_CONFIG=true npx eslint --config tests/eslint_rules.config.mjs tests/unit/video-owner-channel-link.test.js
• node --check js&css/web-accessible/functions.js && node --check tests/unit/video-owner-channel-link.test.js
• git diff --check

Note: running ESLint over the full existing js&css/web-accessible/functions.js still reports pre-existing style issues outside this patch.

[improvedtube-backup]

1. Why was this added (years ago) without depending on a feature being enabled?
   (should probably not. Did it fix a Youtube Bug before ?)

else if (name === 'YTD-VIDEO-SECONDARY-INFO-RENDERER') {
this.elements.yt_channel_name = node.querySelector('ytd-channel-name');
this.elements.yt_channel_link = node.querySelector('ytd-channel-name a');

2. How did Link to Video Owner's Channel not updating when switching videos #1485 happen?

[OnlyYu1996]

因项目不接受 AI 辅助贡献，主动关闭此 PR。抱歉打扰。

[improvedtube-backup]

hi @OnlyYu1996 didn't say so.
You can add disclosure.
And tune your system or make it semi-automated in the meantime.