[Kubernetes] Coerce Python bool tolerations to lowercase for taint match

[rohansonecha]

Summary

Follow-up to #9750. _str_or_empty (used by taint_is_tolerated to
compare toleration values against K8s taint values) coerces non-string
scalars to string so unquoted YAML values like value: 0 and
value: 1.5 still match real K8s taints. But for Python bool,
str(True) produces the Python-cased 'True' — while K8s stores
taint values as whatever Go's YAML serializer emits, which is always
lowercase ('true' / 'false'). Even kubectl taint nodes X foo=true:NoSchedule lands on the node as value: "true".

That silent mismatch means a config

tolerations:
  - key: foo
    operator: Equal
    value: true   # unquoted YAML → Python True → 'True'
    effect: NoSchedule

never matches a real K8s taint with value: "true" — the operator
sees 'True' != 'true' and the taint reads un-tolerated. The user has
to remember to quote the value (value: "true") to work around it.

Special-case bool inside _str_or_empty to lowercase. Mirrors what
Go's strconv.FormatBool / fmt.Sprintf("%t", ...) produce, so the
matcher stays in lockstep with how K8s actually stores taint values.

Test plan

• Updates the yaml-bool / yaml-bool-false parametrize cases in
  test_taint_is_tolerated_str_coercion to use 'true' / 'false'
  taint values (the realistic K8s shape).
• Adds two python-cased-bool-no-match cases asserting the coercion
  is one-directional / strict: a hypothetical taint stored as
  Python-cased 'True' must NOT match a Python-bool toleration. We
  fix the toleration side to match K8s reality, not loosen the
  comparison to be case-insensitive.

pytest tests/unit_tests/kubernetes/test_kubernetes_utils.py -k taint_is_tolerated_str_coercion

🤖 Generated with Claude Code

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[gemini-code-assist]

Code Review

This pull request updates the _str_or_empty utility function in sky/provision/kubernetes/utils.py to explicitly convert boolean values to lowercase strings ('true' or 'false'), aligning with how Kubernetes stores taint values. Unit tests in tests/unit_tests/kubernetes/test_kubernetes_utils.py have been updated and expanded to cover these changes and prevent regressions. There are no review comments, and I have no feedback to provide.

[devin-ai-integration]

✅ Devin Review: No Issues Found

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