native: integrate WordPress query pipeline repairs

[chubes4]

Summary

• integrates source candidates from native: support aliased Meta Query self joins #378, fix: route native multisite prefixes #379, fix: accept native SELECT FOR UPDATE #380, test: restore native coverage probe evidence #381, native: expand scalar projection functions #382, and fix: support native dbDelta schema diffs #383
• reconciles scalar, JOIN, derived-source, boolean, grouping, multisite, dbDelta, coverage, and terminal FOR UPDATE behavior in one typed pipeline
• composes scalar/IN/NOT IN/EXISTS boolean terms and combined-result UNION ordering

Landing Review Repair

• landing review found scalar-filtered bounded subqueries silently ignored their filters and hidden scalar columns
• d79e2ab7c36875965d9b3dd315dc2af1a1143710 loads and evaluates bounded scalar/boolean filters during materialization; unsupported correlated boolean shapes remain fail-closed
• lower-time invalid boolean subqueries now return structured native diagnostics rather than escaping an exception
• focused coverage includes scalar subqueries, joined correlated EXISTS, NULL membership, chained UNION/ALL global order/offset, aliases/ordinals, and UNION FOUND_ROWS

Final Verification

• isolated Git-backed Lab checkout at d79e2ab
• Composer install, complete tests/smoke-*.php sweep, and SQLite differential passed
• Codebox coverage: 45/45 statements and 26/26 operations; artifact SHA-256 000f0a18ecf381df421623ca1b42c979d6eaab376a1310f800e3b28dcf1de5c4
• WordPress lifecycle activation/restart with WooCommerce 11.0.0-dev and native multisite cold reload passed
• native dbDelta and disposable MariaDB WordPress 7.1 dbDelta reference passed all eight assertions
• disposable MariaDB differential matched scalar-filtered IN (0), joined EXISTS (1), NULL NOT IN (0), and chained UNION order/offset (2)

Scope Boundaries

Subqueries remain bounded single-table plans with one qualified equality correlation. Scalar boolean filters without nested subqueries are supported; correlated boolean subquery shapes fail closed. UNION branches require compatible projections; global ORDER BY accepts first-branch output names or positive ordinals.

AI Assistance

Implemented, independently reviewed, and tested with OpenAI GPT-5.6 Terra (openai/gpt-5.6-terra) via OpenCode. I repaired the typed parser/executor path, added focused regressions, and ran the listed isolated Lab workflows.