[MarkParker5]

For review, do not merge yet.

• Kept-key trap (d-key): a node announcing api_encryption while the Hub still holds a key it gave it earlier (soft-unpaired, then reflashed with its own YAML key) is now offered with [none, secret] instead of [none], so the user can enter the new key. none still pairs with the kept key.
• Hub on Ethernet (d-eth): wifi_credentials() returning None (or an SDK without it) makes pair_device of a BLE discovery raise the SDK's MissingCredentialsError with type wifi before any BLE step. The discovery's last_error is left alone: the Hub returns the error to the app's pairing request as a 422 with the kept device_id and credentials_type: "wifi" (ParkerIndustries/MajorDom-Hub#149), and the app retries on that id after the user saves Wi-Fi on the Hub. wifi is the only type this integration raises.
• No README changes: integration docs live in the docs repo.
• Hardware tests are not part of this PR: the earlier tests/hardware changes (cage DUT guard) are reverted here and move to the Hub repo.

Merge order

Depends on MissingCredentialsError from integration-sdk#6, not in any SDK release yet; CI here fails on import until then.

1. Merge integration-sdk#6, release the SDK.
2. Bump majordom-integration-sdk here to that release (pyproject.toml + poetry.lock), and in MajorDom-Hub#149.
3. Merge this together with MajorDom-Hub#149.

Tests

Tests-first: the Hub-Wi-Fi tests now assert last_error stays None and failed (2 failed) before the controller change. With the SDK branch feature/credentials-option installed in the venv: pytest tests 138 passed on Python 3.13, ruff check, ruff format and ty check clean. The hardware test was not run (no cage access).