ci: update actions/cache action to v6

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
actions/cache	action	major	v5.1.0 → v6.1.0

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Release Notes

actions/cache (actions/cache)

v6.1.0

Compare Source

What's Changed

• Bump @​actions/cache to v6.1.0 - handle read-only cache access by @​jasongin in #​1768

Full Changelog: actions/cache@v6...v6.1.0

v6.0.0

Compare Source

What's Changed

• Update packages, migrate to ESM by @​Samirat in #​1760

Full Changelog: actions/cache@v5...v6.0.0

v6

Compare Source

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Configuration

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[github-actions]

common-lint results

✅ Overall: PASSED

🔗 Run: 30145762392 · Commit: 52dbd3c

Check	Result
GitHub Actions lint (actionlint, ghalint, zizmor)	✅ Passed
commitlint	✅ Passed
renovate-check	⊘ Skipped
typos	✅ Passed
vuln-scan (Trivy)	✅ Passed

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1. GitHub Actions lint — ✅ Passed

 INFO zizmor: 🌈 zizmor v1.25.2
 INFO audit: zizmor: 🌈 completed ./.github/workflows/ci.yml
 INFO audit: zizmor: 🌈 completed ./.github/workflows/github-actions-lint.yml
 INFO audit: zizmor: 🌈 completed ./.github/workflows/lint.yml
 INFO audit: zizmor: 🌈 completed ./.github/workflows/nix-vendor-hash.yml
 INFO audit: zizmor: 🌈 completed ./.github/workflows/tagpr.yml
 INFO audit: zizmor: 🌈 completed ./.github/workflows/trivy.yml
No findings to report. Good job! (23 suppressed)

2. commitlint — ✅ Passed

(no output)

3. renovate-check — ⊘ Skipped

No matching files in this change set (renovate.json, renovate.json5, or .github/renovate.json).

4. typos — ✅ Passed

(no output)

5. vuln-scan (Trivy) — ✅ Passed

Summary: No vulnerabilities detected.