fix(backend): close sessions properly

[StarDylan]

No description provided.

[Copilot]

Pull request overview

This PR aims to improve backend session shutdown behavior by ensuring websocket sessions and related background resources are torn down more reliably and with better logging.

Changes:

• Handle websocket disconnects more explicitly and add more robust teardown logging in the websocket endpoint.
• Improve session/task shutdown behavior in the context manager (incl. pyright unused-result cleanup).
• Add EndOfStream handling in TextCoalescer and update the pyright baseline accordingly.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
backend/src/main.py	Refactors websocket receive loop error handling and adds more detailed teardown/error logging.
backend/src/interview_helper/context_manager/session_context_manager.py	Adjusts task group shutdown call to satisfy static analysis.
backend/src/interview_helper/context_manager/TextCoalescer.py	Adds graceful handling for closed streams (anyio.EndOfStream) during coalescing.
backend/.basedpyright/baseline.json	Removes a baseline entry made obsolete by the code change.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.