[RFE] Add Claude Code skill for pre-rebuild graph analysis #1012
Description
Add a Claude Code skill (.claude/commands/pre-rebuild-check.md) that teaches the assistant to run and interpret graph check (#998) results.
The skill encodes the workflow: run fromager graph check, read the three booleans and build efficiency, distinguish collapsible (wasted builds) from required (will fail), identify binding parents, and suggest constraint edits.
Depends on #998. This skill would complete the v0.1 of the analysis check and accompanying skill.