DIS-033: stale/unbuilt .refs.idx makes be log: silently return empty (and be head GRAFFAIL)

A freshly-cloned or freshly-touched worktree can have a stale or not-yet-built <store>/.refs.idx; while it is stale the log/head projectors resolve no --at tip and be log: returns an EMPTY listing (just the banner, exit 0) — looking like "no history" — while be head file://… returns GRAFFAIL "--at sha not set". It self-heals: the next be invocation rebuilds .refs.idx (mtime bumps) and the identical be log: then lists normally. Hit repeatedly this session in the $HOME/todo/DIS-030 clone and earlier loop clones. Per be undo commit procedure a stale .refs.idx is a known cause of GRAFFAIL --at not set; the bug is the silent-empty (and the unbuilt-index gap), not the eventual self-heal. See HEAD, CLAUDE.

Issues

A stale refs index yields no --at, and the projectors disagree on how they fail.

Blockers

None. Needs the projector's .refs.idx read path to detect staleness.

Planned

Rebuild a stale index before resolving cur, or fail loud — never silent-empty.