_blocks/memory-protocol.md references ~/.claude/memory/MEMORY.md, but the
installer previously only scaffolded agents/ hooks/ skills/ — so the first
agent that followed the block would fail reading a non-existent index.
Now mkdir -p ~/.claude/memory and, only when MEMORY.md is absent, write a
minimal placeholder (frontmatter + pointer to the block). User-edited
MEMORY.md is never overwritten.
All three hooks used `set -eu` + `cat | jq …`. Without jq installed, jq
would fail and `-e` would abort the hook → non-zero exit → Claude Code
refuses Edit/Write/Bash system-wide. Now each hook probes for jq BEFORE
`set -eu` and exits 0 silently if absent. Also dropped the useless `cat |`
pipe — `jq -r` reads stdin directly.
Companion: install.sh jq check upgraded from warn to hard `exit 1` because
without jq the hooks are dead weight; message states jq is required on
any machine that will activate the hooks.
Previously cp -f clobbered user-edited _blocks/, _templates/, _assembler/,
hooks/, and skills/ silently — violating the README's "idempotent" claim
on re-run. Now each of those targets is snapshotted to a timestamped
<target>.bak-$(date +%s)/ sibling before overwrite, but only when the
target actually contains regular files (freshly-mkdir'd scaffolds are
skipped). _manifests/ unchanged — already uses per-file skip-if-exists.
Kit source ($KIT_DIR) is never backed up.
