fix(reports): disable optional memory fanout for FeedbackAnalysis by default

[dereknorrbom]

Summary

• Update FeedbackAnalysis (legacy alias) to default memory_analysis to false unless explicitly configured.
• Keep FeedbackAlignment behavior unchanged.
• Add tests to verify:
• default memory analysis is disabled for FeedbackAnalysis
• explicit memory_analysis: true is preserved

Why

• A production report using class: FeedbackAnalysis with days failed after score-result attachments with:
• IndexError: pop from an empty deque
• The failure occurs in async execution after heavy per-score processing; this change keeps legacy FeedbackAnalysis runs on the lightweight path by default and avoids optional memory-analysis fanout unless requested.

Validation

• poetry run pytest -q plexus/reports/tests/test_feedback_analysis_alias.py -q
• poetry run pytest -q plexus/reports/blocks/feedback_alignment_test.py -q

Expected Outcome

• Existing FeedbackAnalysis reports (days/date-window) complete without invoking memory analysis unless explicitly opted in.
• Users who want memory outputs can still enable them via memory_analysis: true.

Kanbus / Task Tracking

• plx-e36b06