Usage-limit checkpoints clean up old git references in one sandboxed step

For its usage-limit feature, Claude Code saves checkpoints in git as references, which are named pointers to saved states. It also removes old ones. Several things changed:

• Old checkpoint references are now removed together in one batch rather than one at a time.
• When sandboxing is on (a sandbox limits what commands can read and change), that removal runs inside the sandbox.
• If removal fails, the log says stopped deleting old checkpoint refs; the next checkpoint retries, and the next checkpoint tries again.
• The path used for resuming is added to the repository's local exclude list, which tells git to ignore it without changing shared files.
• Text that the server supplies for the usage-limit release and resume prompts is now checked before use, and Claude Code reports when it rejects or changes that text.