test(api): check durable provider dependency across releases

[iamgp]

Scope

Make the API dependency contract test valid after release preparation. It currently hard-codes phlo-postgres>=0.16.0,<0.17, so the correctly rewritten >=0.17.0,<0.18 release manifest fails the test.

Parse the mandatory dependencies and assert that PostgreSQL is unconditional. Release-policy and version-drift checks continue to validate the dependency range. No production code, metadata, locks, or excluded PRs change.

This follows #1052, which is merged and has green post-merge release-candidate checks. The release bot refreshed #970 automatically; its only substantive remaining failure is this test. This PR does not merge or edit #970.

Verification

• Reproduced the original assertion failure against the exact refreshed release manifest.
• Corrected test passes against that manifest and rejects both missing and optional-only PostgreSQL dependencies.
• API and release-policy tests: 979 passed, 10 integration tests deselected.
• Ruff, C901, formatting, module headers, and whitespace checks pass.

Keep this follow-up unmerged until separately authorised.

[coldtea-pr-lens]

Note

The title starts with test(api):, so PR Lens left this pull request undrawn. Comment @pr-lens draw to draw it

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