Persist left-menu fold state with first-level defaults

[MariusStorhaug]

Summary

• remove
  avigation.expand so the menu is not force-expanded globally
• add a global nav-state script in .github/docs/nav-state.js`n- load the script through �xtra_javascript with repo placeholders so each repo resolves its own main-branch asset

Behavior

• first-level groups expand by default when no saved state exists
• user fold/unfold choices persist in localStorage across navigation

[github-actions]

No Significant Changes Detected

This PR does not contain changes to files that would trigger a new release:

Pattern	Description
^src/	Matches files where path matches this pattern
^README\.md$	Matches files where path matches this pattern

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[github-actions]

Super-linter summary

Language	Validation result
CHECKOV	Pass ✅
GITHUB_ACTIONS	Pass ✅
GITLEAKS	Pass ✅
GIT_MERGE_CONFLICT_MARKERS	Pass ✅
JAVASCRIPT_ES	Pass ✅
JAVASCRIPT_PRETTIER	Fail ❌
MARKDOWN	Pass ✅
NATURAL_LANGUAGE	Pass ✅
POWERSHELL	Pass ✅
PRE_COMMIT	Pass ✅
SPELL_CODESPELL	Pass ✅
TRIVY	Pass ✅
YAML	Pass ✅

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JAVASCRIPT_PRETTIER

Checking formatting...[�[33mwarn�[39m] .github/docs/nav-state.js
[�[33mwarn�[39m] Code style issues found in the above file. Run Prettier with --write to fix.