/ultrareview: clearer base-branch errors, a spend-limit warning and a review file variable

What

/ultrareview runs a deep code review in the cloud. Several parts of it changed:

• Base branch errors: when the base branch or commit is not found on your computer, Claude Code tries to fetch it and now reports whether the fetch failed, checking origin (the main remote copy of the repository) failed, or the ref does not exist, for example "is not a local branch or commit, and origin couldn't be checked for it." The advice now suggests a refs/heads fetch command instead of always naming git fetch origin with the branch. Nothing has been read about the switch tengu_review_remote_precondition_recovery.
• Fetched commit used: when a commit is recovered this way, it is used as the comparison point, and the empty-diff message says "on origin".
• Spend limit warning: in some cases a new message says "If this review reaches a spend limit set by your organization, it can stop early, with few or no findings, and what it has used stays billed." Before, only the credits-left message existed.
• Review file: the launcher can now pass BUGHUNTER_REVIEW_MD into the review's environment.
• Folder changes: the wrapper around changing folders now records a hasThrown flag.

Why

If your branch name is unusual or not pushed, you are told which step failed and what to fetch. You also learn before a review that an organization spend limit could cut it short while the usage still counts.