feat(pgpm): generate revert/verify scripts for restructured exports

[pyramation]

Summary

Phase 4 follow-up to #1554 (refs constructive-io/constructive-planning#1329): granularity-restructured exports previously emitted empty revert/verify files. This wires the revertFor/verifyFor generators from @pgsql/scripts (constructive-io/pgsql-parser#327, published as @pgsql/scripts@18.0.1) through restructureChanges and pgpm export so every restructured change ships populated, mechanically-derived scripts.

• @pgpmjs/transform — restructureChanges now returns RestructuredChange extends GranularityChange:

  interface RestructuredChange extends GranularityChange {
    revert: string;  // revertFor(groupFacts): inverse statements, reverse topo order within the group, no CASCADE
    verify: string;  // verifyFor(groupFacts): one raise-on-failure existence check per created object
  }

  Generation warnings (e.g. revert not derivable: ... for non-invertible statements) are surfaced in result.warnings, prefixed with the owning change name.
• @pgpmjs/export — restructureExportRows carries change.revert/change.verify into the emitted rows instead of ''. pgpm headers and transaction wrappers are unchanged (they're owned by writePgpmFiles).
• Deps: @pgsql/scripts@^18.0.0 (new), @pgsql/transform@^18.11.0 (facts now carry the raw statement node the generators need).

e2e round-trip

export-granularity.test.ts proves the full loop against Postgres: export at consolidated → deploy → verify passes on the generated checks → revert succeeds and leaves the DB clean (pets_consolidated_public gone), with no CASCADE in any generated script.

pgpm/transform 43/43 and the granularity e2e suite 10/10 pass against the published packages; the 7 failures in other pgpm/export suites are pre-existing on main (confirmed on a clean worktree).

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

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