Add schema-adapter migration workflows 21-24

[khaliqgant]

Summary

• add workflow 21 for MappingSpec pagination and sync spec updates
• add workflow 22 for SchemaAdapter.sync implementation and tests
• add workflow 23 for the round-trip harness and fixture generation
• add workflow 24 for the nango-unauth provider package workflow

Validation

• agent-relay run --dry-run relayfile-adapters/workflows/schema-adapter-migration/21-mapping-spec-pagination.ts
• agent-relay run --dry-run relayfile-adapters/workflows/schema-adapter-migration/22-schema-adapter-sync.ts
• agent-relay run --dry-run relayfile-adapters/workflows/schema-adapter-migration/23-round-trip-test-harness.ts
• agent-relay run --dry-run relayfile-adapters/workflows/schema-adapter-migration/24-nango-unauth-provider.ts

Notes

• the stricter 00b batch-review rerun is still pending separately and is not included in this PR
• local generator / review artifact changes were intentionally left out of this branch

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.