fix: support GitHub's current repository sidebar

[yankay]

Brief Information

This pull request is in the type of (more info about types):

• build
• ci
• docs
• feat
• fix
• perf
• refactor
• test

Related issues:

• N.A.

Details

GitHub's current React/Primer repository sidebar no longer uses the legacy Layout-sidebar and BorderGrid structure.

This PR:

• locates the sidebar using stable semantic markers
• mounts Activity & OpenRank Trends in the current sidebar container
• injects OpenDigger labels into the current topics group
• remounts injected content when React hydration replaces the sidebar
• adds regression coverage for the current layout and remount behavior

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA

Others

Tests:

• npm test — 90 passed
• Relevant Playwright E2E tests — 4 passed

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