Cloud session git snapshot: new tampered and legacy_tree errors

What

When a cloud session starts from your local repository, Claude Code takes a snapshot of your git data to upload. Unusual repositories used to fail with a generic git error such as "HEAD could not be read back as the commit its id names". Now:

• tampered is a new error for a stored git object that does not match its id. It says "something other than git wrote an object into this .git" and tells you to remove it or re-clone, then start a new cloud session there.
• legacy_tree is a new error for a tree (git's record of a folder) stored in a form git can read but no longer writes. It tells you to commit a change so git rewrites it. An unreadable result with this cause is now handled the same way as the other and host_config causes.
• The cause mapper now passes both tampered and legacy_tree through as named causes.
• Commit listings that come back unreadable or too large are now reported as unreadable. Before, any listing that was not ok was reported as absent.
• write-tree now runs with --ignore-cache-tree, and the comparison between your staged files and HEAD uses a built-in helper instead of running git diff-tree.

The upload path involved sits behind the server-side flag tengu_ccr_bundle_upload, which has not been read.

Why

If your repository has an odd or old object format, or something other than git has written into .git, you now get a specific reason and a concrete fix instead of a vague git error.