fix(copaw): fall back to static mc alias in local k8s mode

[RerankerGuo]

Summary

This PR fixes #957 by adding a fallback path in _ensure_alias() for local K8s deployments with self-hosted MinIO.

Problem

In v1.1.2, commit fc1b934 added k8s mode detection that unconditionally skipped mc alias setup when AGENTTEAMS_RUNTIME=k8s. This assumed mc-wrapper.sh would always provide STS credentials via MC_HOST_* environment variables. However, this assumption only holds for Aliyun cloud deployments (RRSA/STS).

In local K8s deployments with self-hosted MinIO:

1. HICLAW_RUNTIME=k8s → k8s mode = True → alias setup skipped
2. mc-wrapper.sh does not set MC_HOST_hiclaw (no STS provider)
3. mc mirror hiclaw/... fails with alias not found
4. copaw-worker startup fails

Fix

When AGENTTEAMS_RUNTIME=k8s, check if MC_HOST_{alias} is already set:

• If set (cloud STS mode): skip alias setup as before
• If not set (local K8s): fall through to the static mc alias set path

Changes

• copaw/src/copaw_worker/sync.py: Modified _ensure_alias() to conditionally skip in k8s mode
• copaw/tests/test_sync.py: Added 3 unit tests covering:
  1. k8s + MC_HOST set → skip static (cloud STS)
  2. k8s + MC_HOST not set → fall through to static (local MinIO)
  3. non-k8s → use static (unchanged behavior)

Testing

• pytest tests/test_sync.py::test_ensure_alias_k8s_with_mc_host_set_skips_static PASSED
• pytest tests/test_sync.py::test_ensure_alias_k8s_without_mc_host_falls_through_static PASSED
• pytest tests/test_sync.py::test_ensure_alias_non_k8s_uses_static PASSED

[gemini-code-assist]

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