test: refresh PostgreSQL correctness snapshot after review fixes

Regenerate the PostgreSQL 18.4 expected results, compact CI fixtures and
compatibility report against implementation commit 3a98211. Preserve the
pinned versions, original source SQL, extraction policy, deduplication and
source provenance.

Deep support increases from 49,845 to 49,848 of 51,415 statements (96.95%).
The three additions are SAVEPOINT settings and both ROLLBACK TO settings
spellings, now accepted through the shared PostgreSQL ColId identifier rule.
There are no lost deeply supported statements. Remaining totals are 1,041
errors, 377 trailing-input cases, 97 type mismatches and 52 partial results.

Compare every refreshed row with the reviewed original-source replay, including
parser status, statement mappings, AST presence and unconsumed input. All
51,415 rows agree. All three additions and 653 existing affected alias/DML
statements preserve PostgreSQL raw ASTs after SQL reconstruction, ignoring
source-position metadata only.

The complete pinned compatibility workflow passes against this snapshot,
including all 5,122 generated CI cases. This is a correctness baseline refresh;
no benchmark sources, reports or benchmark-only documentation are included.

Author: renecannao