Summary

• Renames SPLUNK_AO_LOG_STREAM → SPLUNK_AO_AGENT_STREAM and SPLUNK_AO_LOG_STREAM_ID → SPLUNK_AO_AGENT_STREAM_ID across all source, test, example, and documentation files, following the
  domain entity rename from HYBIM-730 (PR feat: hard cut-over — rename LogStream→AgentStream, Metric→Evaluator #100)
• Adds a silent backward-compat fallback in src/splunk_ao/utils/env_helpers.py: if SPLUNK_AO_AGENT_STREAM / SPLUNK_AO_AGENT_STREAM_ID are unset, the old variable names are read instead,
  so existing user environments continue to work without changes
• Updates the _BRIDGE in config.py to map the new names to GALILEO_LOG_STREAM / GALILEO_LOG_STREAM_ID for galileo-core compatibility
• The underlying API endpoints (/log_streams) are unchanged — this is a client-side rename only

Test plan

• uv run pytest tests/ splunk-ao-adk/tests/ splunk-ao-a2a/tests/ passes with the renamed env vars
• uv run mypy src/splunk_ao/ reports no new errors
• Verify that setting the old SPLUNK_AO_LOG_STREAM still works (backward-compat alias in env_helpers.py)