fix: use valid isinstance tuple syntax for list/tuple checks in Prometheus result flattening

[Copilot]

isinstance(x, list | tuple) raises TypeError at runtime — the | union operator is valid for type annotations but not for isinstance() type arguments. This broke all Prometheus result flattening across matrix, vector, and scalar/string result types.

Changes

• query_prometheus.py: Replace all three isinstance(..., list | tuple) calls in _flatten_prometheus_result with isinstance(..., (list, tuple))

# Before — raises TypeError at runtime
if not isinstance(point, list | tuple) or len(point) != 2:

# After — correct tuple syntax
if not isinstance(point, (list, tuple)) or len(point) != 2:

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[Copilot]

Pull request overview

This PR fixes a critical runtime bug in the Prometheus result flattening logic where incorrect isinstance() syntax was causing TypeError exceptions. The issue affected all three Prometheus result types (matrix, vector, and scalar/string).

Changes:

• Fixed isinstance() calls to use proper tuple syntax (list, tuple) instead of invalid union syntax list | tuple