Protect against Notes_Helper fatal errors during plugin updates

[agibson-godaddy]

Summary

This adds some various protection measures to avoid Notes_Helper fatal errors during plugin updates, which is when the framework namespace changes.

Fixes #824

Story: MWC-19419

Release: #825 (release PR)

QA

• Code review
• Checks pass

Before merge

• I have confirmed these changes in each supported minor WooCommerce version

[Copilot]

Pull request overview

This PR hardens the framework against fatal errors triggered during plugin updates via /wp-admin/update-core.php, where versioned framework namespaces can change mid-request and cause Notes_Helper class resolution failures.

Changes:

• Guard Notes_Helper usage during deactivation with class_exists() to avoid upgrade-time fatals.
• Widen the gateway notice creation try/catch from \Exception to \Throwable and add a class_exists() guard before calling Admin\Notes_Helper::note_with_name_exists().
• Add a changelog entry for the fix.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
woocommerce/Plugin/Lifecycle.php	Adds a class_exists( Notes_Helper::class ) guard before deleting admin notes during deactivation to prevent upgrade-time fatals.
woocommerce/payment-gateway/class-sv-wc-payment-gateway-plugin.php	Catches \Throwable around note creation and guards note-deletion checks with class_exists() to prevent namespace-mismatch fatals during updates.
woocommerce/changelog.txt	Documents the fix for Notes_Helper fatal errors during plugin upgrades.

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