refactor: rename SplunkAOMetrics to SplunkAOEvaluators (HYBIM-949)

[shuningc]

Summary
Renames the built-in scorer enum SplunkAOMetrics → SplunkAOEvaluators (HYBIM-949) to align with the evaluators domain terminology introduced in the HYBIM-730 rename.

This is a hard cut-over: no backward-compatibility alias for SplunkAOMetrics.

Changes
Rename enum class in src/splunk_ao/schema/metrics.py
Update public export in src/splunk_ao/init.py
Update type hints and usages in SDK modules (agent_stream, agent_streams, evaluator, experiment, experiments, types, utils/metrics)
Update tests, examples, migration-tool docs, and domain-rename doc examples

[fercor-cisco]

🤖 This review was generated by the Astra agent (claude-opus-4-8). It may contain mistakes.

Verdict: approve — Complete, consistent mechanical rename of SplunkAOMetrics→SplunkAOEvaluators; no stale references remain and tests/exports updated.

Follow-ups

Suggested follow-up work that could be tracked as Jira tickets:

• tests/schemas/test_metrics.py:18-33: Test function names still read test_galileo_metrics_* despite the enum now being SplunkAOEvaluators and the Galileo prefix having been dropped in prior renames. Renaming these to test_evaluators_* would keep test naming aligned with the domain terminology. Non-blocking, cosmetic.
• src/splunk_ao/schema/metrics.py:15-15: The SplunkAOEvaluators docstring still says 'Built-in Splunk AO metric scorers.' Consider updating the wording to 'evaluators' to match the new domain terminology. Non-blocking.

[fercor-cisco]

Filed follow-up stories under epic HYBIM-697 for the cosmetic items deferred from this rename:

• HYBIM-955 — Rename test_galileo_metrics_* tests to test_evaluators_* (tests/schemas/test_metrics.py:18-33).
• HYBIM-956 — Update the SplunkAOEvaluators docstring to say "evaluators" instead of "metric scorers" (src/splunk_ao/schema/metrics.py:15).