Diskless sessions skip local file reads and writes

What

Claude Code is gaining a diskless mode, where a session has no local storage to read from or write to. When the same internal check is true:

• The auto-mode classifier dump, the session title file and the scoping record for forked skills are not written. The scoping record reports diskless with not written: no storage backend, or no key for the target path.
• Taking over an agent whose record is diskless now fails with an error.
• Skill folders are not scanned, except for policy settings, and the log says the session is diskless, so no skills load from it.
• Uploading the home-directory inventory is skipped with reason diskless.
• The environment details sent at session start report the shell as none.
• Two file readers report the file as absent.

Separately, the spare background job gains a guard that looks like a check for Claude Code exiting.

Why

This prepares Claude Code to run where there is no local disk, such as a hosted session. In that mode, skills and local files will not load.