Fix traversal of semantic AST children

[git-hulk]

Summary

• Traverse semantic AST children that were skipped by both Accept and Walk: ColumnDef.CompressionCodec, TTLPolicyRule.Action, and WithTimeoutClause.Expr.
• Make WithTimeoutClause tolerate expression-backed values in End, Accept, and formatting.
• Add a static traversal drift guard for semantic AST fields so future omissions are caught even when both traversal engines miss the same field.

Verification

• go test ./parser -run 'TestTraversalEnginesVisitAllSemanticFields|TestTraversalEnginesVisitSameFields|TestTraversalVisitsJSONTypeOptions|TestVisitJoinTableExprWithSampleRatio|TestWalkVisitsInsertValues|TestDestinationTableSchemaVisitedOnce'
• go test ./...
• git diff --check
• make test

Notes

• make lint currently fails before linting because the local golangci-lint cannot load this repo config: unsupported version of the configuration: "".
• SQL rewrite / Transform implementation work is intentionally excluded from this PR for separate review.

[chatgpt-codex-connector]

Codex usage limits have been reached for code reviews. Please check with the admins of this repo to increase the limits by adding credits.
Repo admins can enable using credits for code reviews in their settings.