Install hooks into the repo's own hooks dir, ignoring core.hooksPath

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/install-hooks.sh

@@ -5,10 +5,13 @@
 # (and so their hooks) run outside the sandbox. Re-run after changing anything in .githooks/.
 set -e
 cd "$(dirname "$0")/.."
-if ! hooks=$(git rev-parse --git-path hooks 2>/dev/null); then
+# Use the repo's own hooks directory, not `git rev-parse --git-path hooks`: that follows a
+# (possibly global) core.hooksPath and would install these hooks for every repo.
+if ! common=$(git rev-parse --git-common-dir 2>/dev/null); then
   echo "install-hooks: not a git checkout; skipping." >&2
   exit 0
 fi
+hooks="$common/hooks"
 mkdir -p "$hooks"
 for hook in .githooks/*; do
   cp "$hook" "$hooks/"