feat(scripts): @pgsql/scripts — revert and verify generation from statement facts

[pyramation]

Summary

Phase 4 follow-up (refs constructive-io/constructive-planning#1329): a new package, @pgsql/scripts, derives revert and verify scripts from @pgsql/transform statement facts — the missing third leg next to the parser and deparser. Consumed by constructive-io/constructive#1562 so pgpm export --granularity stops emitting empty revert/verify files.

revertFor(facts: StatementFacts[]): GeneratedScript  // { sql, warnings }
verifyFor(facts: StatementFacts[]): GeneratedScript

• revertFor — mechanical inverses in reverse topological order of buildStatementGraph(facts), so dependents drop before dependencies and no CASCADE is ever emitted. Inverses are built as AST nodes and deparsed (never string-templated): CREATE schema/table/view/index/sequence/type/domain/function/trigger/policy/extension/role → DROP (functions keep their input signature for overload safety); ADD COLUMN/ADD CONSTRAINT → DROP; GRANT → REVOKE; RLS enable/force → disable/no-force; COMMENT ON → ... IS NULL. Non-invertible statements (DML, dynamic SQL, ALTER ... SET with unknown prior state, unnamed constraints, REVOKE) emit -- revert not derivable: <reason> plus a warning — never guessed.
• verifyFor — one raise-on-failure existence check per created object via SELECT 1/(CASE WHEN <exists> THEN 1 ELSE 0 END);: to_regclass/to_regprocedure/to_regtype where a reg* cast exists, catalog lookups (pg_policies, pg_trigger, pg_extension, pg_roles, pg_auth_members, information_schema.columns/table_constraints) for the rest, has_table_privilege/has_function_privilege/has_schema_privilege for grants.
• The supported vocabulary is exported (SUPPORTED_STATEMENTS, SUPPORTED_NODE_TAGS) and documented as a table in the package README — consumers can check support programmatically instead of only hitting warnings.

Supporting changes in @pgsql/transform:

• StatementFacts.stmt? now carries the raw parsed statement node so consumers can derive statements without a second parse.
• Fixed CreateDomainStmt classification: the domain's name is domainname (typeName is its base type).

45 exact-output unit tests in packages/scripts/__tests__/invert.test.ts; @pgsql/scripts added to the CI test matrix.

Link to Devin session: https://app.devin.ai/sessions/7f032c8e1bf245eeac2def99fdcc1623
Requested by: @pyramation

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