test: skip quoting-engine strategy tests when private module is absent

[shuofengzhang]

What changed

• Added a requires_quoting_engine skip marker in tests/test_engine_strategies.py that checks whether ~/Tee-work-/quoting_engine exists.
• Applied that marker to strategy test classes that import private quoting-engine-backed strategies (engine_mm, funding_arb, regime_mm, liquidation_mm).
• Kept registry tests active so OSS environments still validate strategy registration behavior.

Why

• These tests currently hard-fail in OSS/dev environments without the private quoting_engine checkout, even though the repo documents open-source alternatives.
• Skipping only the private-dependency strategy tests prevents false-red test runs for external contributors while preserving coverage for testable OSS paths.

Insight / Why this matters

• Root cause: strategy tests import modules that unconditionally raise ImportError when a local private path (~/Tee-work-/quoting_engine) is absent.
• Why it is easy to miss: maintainers with private dependencies checked out won't see failures; outside contributors and clean CI/dev setups do.
• Tradeoff: we trade strict execution of private-dependent tests for portability. This is scoped: only tests requiring the private module are skipped.
• Impact: contributors can run the public test suite without local private infra, reducing contributor friction and false failure triage.

Practical gain / Why this matters

• Immediate practical gain: pytest is no longer blocked by private-only imports in standard OSS environments.
• Beneficiaries: external contributors, new maintainers, and any CI/dev setup without quoting_engine checked out.
• Likely maintainer acceptability: low-risk, narrowly scoped change that improves test reliability without touching runtime strategy logic.

Testing

• Reproduction before change:
  • scripts/clone_and_test.sh Nunchi-trade/agent-cli
  • Result: 20 failed, 580 passed (failures due to missing ~/Tee-work-/quoting_engine).
• Validation after change:
  • source .venv/bin/activate && pytest -q tests/test_engine_strategies.py
  • Result: 3 passed, 20 skipped
  • scripts/clone_and_test.sh Nunchi-trade/agent-cli
  • Result: 580 passed, 20 skipped

Risk analysis

• Scope limited to test code only; no production behavior changes.
• Skip condition is explicit and deterministic (filesystem path check).
• Rollback-safe: removing the decorator block restores previous behavior.