chore: finalize PowerLens 0.9.4 release

[progresshans]

Summary

• add the final 0.9.4 security release notes to main
• prepare the verified Sparkle 2.9.6 build for the stable v0.9.4 tag

Release validation

The same develop commit was published as v0.9.4-alpha.3 and independently verified:

• signed and notarized release workflow passed
• ZIP and DMG checksums passed
• nested code signatures and Gatekeeper assessment passed
• app and DMG notarization tickets passed
• arm64 app bundle embeds Sparkle 2.9.6
• macOS 26, Xcode 27, and package smoke CI passed

After this PR is merged, v0.9.4 will be tagged on the exact resulting main commit and the stable appcast will be verified.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-29T07:46:41.384262Z	066da93	PR opened

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