Add workflow spine end-to-end sqlite smoke test

[akgohain]

Motivation

• Add a deterministic backend-level smoke test that validates the core workflow spine sequence (get/create current workflow, append events, create agent proposal, approve proposal, and verify state/event transitions).
• Keep the test isolated from application state so it can run reliably in CI and local environments using only a local SQLite setup.

Description

• Add tests/test_workflow_spine_smoke.py which implements a private in-memory SQLite schema and a single end-to-end smoke test exercising the workflow spine contract.
• Include lightweight test-local helpers: _get_or_create_current_workflow, _append_event, _create_agent_proposal, and _approve_proposal to emulate workflow/event/proposal behavior without touching production code.
• Assert deterministic sequence numbers for appended events and the final workflow state to ensure no flaky timing assumptions.
• This is a test-only change and does not modify any production files.

Testing

• Ran pytest -q tests/test_workflow_spine_smoke.py which passed (1 passed).
• Attempted uv run pytest -q tests/test_workflow_spine_smoke.py which failed due to environment metadata resolution for the editable pytorch_connectomics dependency (missing pyproject.toml/setup.py) and is unrelated to the test logic.

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Codex Task

[akgohain]

Consolidated into draft PR #165 (feat/codex-wave-integration). Closing this source draft to keep review in one place.