Performance: screen-gate assets, cache hot paths, asset bug fixes

[cbravobernal]

Lower-risk half of the performance audit, split out from #466 so it can be reviewed and merged without waiting on multilingual testing. The sibling-field priming (the one change that touches the field-value load path and interacts with WPML/Polylang/ACFML) is in its companion PR. Everything here is behavior-identical or a straight bug fix.

PHP runtime

• Per-request cache for acf_get_option_meta(), invalidated via core option hooks. Keeps the esc_like() hardening from Use esc_like() when building option-meta LIKE patterns #462 — the cache wraps that query, it does not revert it.
• Decode each local JSON file once per request instead of 4× (includes/local-json.php): ~44ms → ~16ms at 200 files. The cache lives in a registered store (resettable in tests/long processes), skips missing files, and save_file()/delete_file() call clearstatcache() so same-request re-reads see fresh contents.
• acf_decode_taxonomy_term(): raw SQL → get_term(), hardened against get_term() returning a truthy WP_Error (ambiguous shared terms / unregistered taxonomies).
• Blocks save-path early bail when no block types are registered.
• Enqueue the escaped-html notice assets at render time inside the notice callback (the script is footer-loaded), so the notice and its JS stay paired and the should-show check runs once.

Assets / enqueue

• scf-bindings moved to enqueue_block_editor_assets (was pulling the wp-editor stack onto classic admin + front-end acf_form pages). The new path keeps trunk's WP 6.7+ guard and now also honors the enable_block_bindings setting (matching Bindings_Editor), so the client never registers the acf/field source when the server doesn't — with a regression test.
• Command-palette scripts gated on wp-commands being enqueued.
• Drop wp-polyfill from all handles (webpack injectPolyfill). Compiled assets are gitignored and rebuilt at release (bin/prepare-release.php), so this takes effect on the next release build.
• Fix pro CSS min suffix (production was shipping unminified CSS).
• Gate acf-pro-ui-options-page with is_admin().
• Fix acf-dark stylesheet 404 by registering it through the central asset path patterns (the hand-built path drifting from the build layout is what caused the 404).
• Trim release zip (exclude assets/src + source maps): −4.2 MB.

Verification

• Rebased onto trunk (6.9.1).
• composer test:php: OK (2846 tests, 21612 assertions). npm run test:unit: 951. composer test:phpstan: clean.
• New code stamped @since SCF 6.9.2; new functions use the scf_ prefix.

See #466 (superseded by this PR + the sibling-priming PR).

Use of AI Tools

Initial implementation by Claude Code (Claude Fable 5) under human direction; split, reviewed and revised by Claude Code (Claude Opus 4.8); multi-agent review findings (bindings gating, WP_Error hardening, notice render-time enqueue, store-backed JSON cache, conventions) addressed by Claude Code (Claude Fable 5). All changes human-reviewed.