Reduce WebSocket connect latency by removing redundant session fetch

[Copilot]

The request was to review the backend for optimization opportunities and address concrete issues with minimal risk. This change targets a hot-path inefficiency in interview WebSocket session startup.

• Optimization: collapse duplicate session reads in connect()

  • InterviewConnectionManager.connect() previously queried SessionModel twice back-to-back for the same session_id:
    • once to set status = "active"
    • again to read interview_type
  • It now performs a single fetch and reuses that entity for both operations.

• Behavior preserved

  • Session activation still occurs at connect time.
  • interview_type derivation logic and downstream panel/solo branching remain unchanged.
  • Persona selection and interviewer metadata persistence flow are untouched.

result = await db.execute(select(SessionModel).where(SessionModel.id == self.session_id))
sess = result.scalar_one_or_none()
if sess:
    sess.status = "active"
    await db.commit()
    interview_type = getattr(sess, "interview_type", "solo") or "solo"

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