feat: Add seed.pgpm() adapter and pgpm integration tests

[pyramation]

Summary

Adds a seed.pgpm() adapter that allows Python tests to use pgpm (PostgreSQL Package Manager) for database migrations without rewriting pgpm in Python. This implements "Option 1" from the integration discussion - treating pgpm as a CLI tool called via subprocess.

Key changes:

• New PgpmSeedAdapter class that calls pgpm deploy via subprocess, passing database connection info through environment variables
• Pre-scaffolded pgpm workspace fixture (tests/fixtures/pgpm-workspace/) with a test module
• Integration tests demonstrating the full flow with @pgpm/faker
• Separate GitHub Actions workflow (test-pgpm.yml) for pgpm integration tests
• Regular test workflow excludes pgpm tests (they require Node.js/pgpm)

Updates since last revision

• Added package parameter to seed.pgpm() to specify which package to deploy, avoiding interactive prompts in CI/non-interactive environments
• Enabled verbose logging in pgpm workflow (-s --log-cli-level=INFO) for better debugging
• Both CI workflows now pass

Review & Testing Checklist for Human

• Verify package parameter usage - The package parameter is required to avoid pgpm's interactive "Choose a package to deploy" prompt. Without it, pgpm may hang in non-interactive environments.
• Check subprocess security - The adapter passes PGPASSWORD via environment variables to subprocess. Verify this is acceptable for your security requirements.
• Verify pgpm fixture structure - The fixture was created by examining existing pgpm workspaces, but should be validated against actual pgpm requirements.
• Note: cache parameter is not implemented - The adapter accepts a cache parameter but it's not yet functional (documented in docstring).

Test plan:

1. Verify both CI workflows pass (regular tests + pgpm integration tests)
2. Check that all 3 tests in test_pgpm_integration.py actually execute (not skipped)
3. Optionally test locally: cd tests/fixtures/pgpm-workspace/packages/test-module && pgpm install @pgpm/faker, then run poetry run pytest tests/test_pgpm_integration.py -v

Notes

• Requires Node.js and pgpm CLI installed (npm install -g pgpm)
• The workflow uses ghcr.io/constructive-io/docker/postgres-plus:17 image consistent with other workflows
• pgpm version pinned to 2.7.9 in the workflow

Link to Devin run: https://app.devin.ai/sessions/1203eea9373240d797329ae288ab6dd7
Requested by: Dan Lynch (@pyramation)

[devin-ai-integration]

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