commit_session endpoint uses QueryParam — optional body fields silently ignored

Same regression as BA-5496. POST /session/{session_name}/commit handler uses QueryParam[CommitSessionRequest] instead of BodyParam.

All fields are optional (login_session_token, filename), so validation passes with empty query params — no 400 error. However, if clients send these values in the JSON body (e.g. WebUI), they are silently ignored because the handler only reads from query string.

Root cause: BA-4823 (PR #9588, fc0caf8eb) bulk-changed BodyParam to QueryParam for multiple session endpoints.

Fix:

- handler.py: Change QueryParam[CommitSessionRequest] to BodyParam[CommitSessionRequest], update query.parsed to body.parsed

- client/v2/domains/session.py: Change params= back to request= in commit_session method

Related: BA-5496 (rename_session), BA-5497 (convert_session_to_image)

JIRA Issue: BA-5511

Start in handler.py at the POST /session/{session_name}/commit handler and compare its parameter parsing with the issue description. Then inspect client/v2/domains/session.py and the related session endpoints; done means JSON body values for login_session_token and filename are validated and sent through the client rather than silently ignored as query parameters.

Written by the indexing model from the issue text.