Ask for the session's latest checkpoint to be pushed

Pins the session's latest committed checkpoint: its checkpoint_revision, the git_commit its verified manifest names, the repository and the target branch. The commit cannot be chosen. checkpoint_revision (default: the latest committed one) may name the revision you looked at; it is refused as checkpoint_moved once a newer one has been saved. Work the session did after that revision may not be in it. repository_id (default: the session's own) may name another catalog repository the session's release lists in github.repositories and its profile allows; the session's workspace has it as a git remote of that name. branch (default: none) makes the target agent/<session-id>-<branch> instead of agent/<session-id>, so one session can push to several branches, each its own pull request. The request starts requested and nothing is pushed until a holder of sessions:approve approves it (POST .../push-requests/{push_request_id}/approve); the push itself is the platform's, never the worker's.

A session has at most one open request (requested, approved or pushing) per repository and branch; there is no limit on how many it makes. Every attempt, refused ones included, leaves a request_push receipt naming the repository and branch; a refusal's error.details.receipt_id names it. A replayed Idempotency-Key answers the request it created.

Scope: sessions:write (API key or cookie session). Idempotency-Key: required.