Improve native SQL and WordPress workload compatibility

[chubes4]

Summary

Incremental native SQL and WordPress compatibility improvements for #377. This PR does not complete MySQL parity or close that tracker.

• Expand bounded metadata/catalog and tableless scalar reads, JSON validation, SQL field descriptors, LIMIT/OFFSET, index hints, column aliases, schema-aware JOIN binding, grouping, and conditional aggregates.
• Preserve temporary schema lifecycle and permanent DDL transaction boundaries; support atomic multi-action ALTER and temporary core-table writes.
• Share connection SQL-mode/default diagnostics and implement typed duplicate-key assignments.
• Support schema-validated non-indexed snapshot filtering and scalar UPDATE assignments with correct nested AND/OR precedence.
• Share row-local scalar evaluation between reads and writes, preserve integer precision within the signed integer domain, and validate assignments before canonical writes. Reject repeated UPDATE targets and unsupported Markdown-post scalar mutations explicitly.
• Retain bounded optional shadow diagnostics and independent authoritative snapshot evidence.

Verification

Exact tested head: 8e49a8a66db2806045e51ecc3d09f905a5602fa0, including current main aa184ca and local scalar UPDATE repair 8f50078.

Unmodified consumer acceptance, WordPress 7.1 / PHP 8.3, managed multisite PHPUnit and shared WP-CLI harness, explicit native candidate source, without diagnostic preload:

Run	Passed	Failed/Error	Skipped	Total
Native Ticketmaster workflow	39	0	0	39
Native full suite	1025	19	9	1053
MySQL full control	1046	0	7	1053

JUnit identity comparison against 6b10e4a confirms the scheduled fanout parent-completion failure is fixed, with no new failures. Real AI parking/resume and scheduled child fanout workflows now both pass.

Targeted repo-native regression commands:

php tests/smoke-native-table-write.php
php tests/smoke-native-write-subquery.php
php tests/smoke-native-transactions.php
php tests/smoke-native-core-table-write.php
php tests/smoke-native-join-query.php
php tests/smoke-native-scalar-projection.php
php tests/smoke-native-aggregates.php
php tests/smoke-native-markdown-post-write.php
git diff --check

Persisted-state tests cover eligible versus active leases, left-to-right assignments, replay rejection, AND/OR precedence, unknown columns, later-row validation failure without partial writes, unique-key rejection, rollback, and integers above floating-point exact precision.

Operator-retained acceptance run names: scalar-update-ticket-native-8e49a8a, scalar-update-full-native-8e49a8a, and scalar-update-full-mysql-control. Each retains the effective recipe, source revision, structured test results and full PHPUnit JUnit XML. These are local operator artifacts, not publicly hosted evidence; the commands above reproduce the owning-layer regressions from this repository.

Remaining Scope

The 19 remaining consumer failures retain their previous identities: four physical-mysqli requirements and fifteen engine-gated identity/upsert outcomes. No fake InnoDB label or weakened consumer assertion is introduced. Native does not provide physical mysqli sessions or full InnoDB/MVCC semantics. Scalar aggregate support, SQL modes, numeric coercion/overflow, temporary session lifetime, and other SQL families remain bounded rather than complete MySQL compatibility.

No release or deployment is part of this merge. Performance work remains deferred.

AI Assistance

OpenAI GPT-6 Astra (openai/gpt-6-astra) via OpenCode implemented and reconciled the latest SQL repairs, reviewed local changes, ran regressions and remote native/MySQL acceptance, compared JUnit failure identities, and prepared this merge at the maintainer's direction. Earlier work in this branch also used OpenAI GPT-5.6 Terra via OpenCode.