Prepare 6.8.9 Release

[cbravobernal]

Prepares the 6.8.9 patch release. Version bumped to 6.8.9; the Stable tag in readme.txt is intentionally left at 6.8.8 and will be flipped after the wp.org build is smoke-tested (per the release process).

Changelog (6.8.9)

Security

• Hardened the escaping of wp_options LIKE queries used when loading option-page meta and during taxonomy term cleanup, switching to esc_like() so option-name prefixes are always matched as literals rather than as patterns.

Fixes

• The URL, text, textarea, and select-style fields no longer raise PHP errors when a non-scalar value (such as an array) is submitted; such input is now treated as invalid.

Contents (already merged to trunk)

• Use esc_like() when building option-meta LIKE patterns #462 — esc_like() in acf_get_option_meta()
• Escape remaining wp_options LIKE patterns with esc_like() (parity follow-up to #462) #467 — esc_like() parity for the taxonomy-form DELETE and the 5.5.0 upgrade SELECT
• Guard URL field against non-scalar values #463 / Guard text field maxlength check against non-scalar values #464 / Guard select field update_value against nested-array values #465 — URL / text+textarea / select non-scalar input guards
• Add backslash coverage to wp_options LIKE escaping tests #468, Add comprehensive regression-test battery across PHPUnit, Jest, and E2E #450 — supporting tests (not shipped to wp.org)

Notes

• Generated by composer prepare-release; only the version bump and changelog are in this PR (build artifacts are gitignored; docs/translations were already current).
• Stable tag flip and the wp.org SVN deploy are handled separately after merge + smoke test.

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