chore: add post-push hook to auto-refresh kyberforge plugin cache

Installing kyberforge via the holocron marketplace caches the plugin at a
specific version. After every push, the marketplace clone and plugin cache
need to be refreshed manually — otherwise new skills added since the last
install are invisible until the user runs `claude plugin update` manually.

Adds a post-push git hook that pulls the holocron marketplace clone and
updates the kyberforge cache automatically after every push, eliminating
the manual refresh step.

## Implementation Notes
- `scripts/git-hooks/post-push` is the canonical source; `install.sh` now
  copies all files in `scripts/git-hooks/` into `.git/hooks/` on fresh
  checkouts, making the pattern extensible for future hooks.
- Hook exits 0 on all failures (warns to stderr) — a stale cache refresh
  never blocks a completed push.
- 11 bats tests cover both the hook and the install.sh copy block, using
  mocked binaries and a temp-tree fixture to avoid touching real state.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01P87CiC58Ru2PPWYTeXtjHT

tests/test-post-push.sh

@@ -0,0 +1,108 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+PASS=0
+FAIL=0
+
+pass() { echo "  PASS: $1"; PASS=$((PASS + 1)); }
+fail() { echo "  FAIL: $1"; FAIL=$((FAIL + 1)); }
+
+HOOK="$REPO_ROOT/scripts/git-hooks/post-push"
+FAKE_BIN="$(mktemp -d)"
+FAKE_HOME="$(mktemp -d)"
+trap 'rm -rf "$FAKE_BIN" "$FAKE_HOME"' EXIT
+
+# Helper: write a fake git stub that exits with the given code
+make_git() {
+  local exit_code="$1"
+  printf '#!/usr/bin/env bash\nexit %s\n' "$exit_code" > "$FAKE_BIN/git"
+  chmod +x "$FAKE_BIN/git"
+}
+
+# Helper: write a fake claude stub; optionally touches a sentinel file on invocation
+make_claude() {
+  local exit_code="$1"
+  local log="${2:-}"
+  if [[ -n "$log" ]]; then
+    printf '#!/usr/bin/env bash\ntouch "%s"\nexit %s\n' "$log" "$exit_code" > "$FAKE_BIN/claude"
+  else
+    printf '#!/usr/bin/env bash\nexit %s\n' "$exit_code" > "$FAKE_BIN/claude"
+  fi
+  chmod +x "$FAKE_BIN/claude"
+}
+
+# Run the hook with mocked PATH and HOME; suppress all output
+run_hook() {
+  PATH="$FAKE_BIN:$PATH" HOME="$FAKE_HOME" bash "$HOOK" > /dev/null 2>&1
+}
+
+# Run the hook and capture combined stdout+stderr
+capture_hook() {
+  PATH="$FAKE_BIN:$PATH" HOME="$FAKE_HOME" bash "$HOOK" 2>&1 || true
+}
+
+# ---------------------------------------------------------------------------
+echo "--- post-push: always exits 0 ---"
+# ---------------------------------------------------------------------------
+
+make_git 1; make_claude 0
+if run_hook; then
+  pass "exits 0 when git pull fails"
+else
+  fail "should exit 0 when git pull fails"
+fi
+
+make_git 0; make_claude 1
+if run_hook; then
+  pass "exits 0 when claude plugin update fails"
+else
+  fail "should exit 0 when claude plugin update fails"
+fi
+
+# ---------------------------------------------------------------------------
+echo ""
+echo "--- post-push: success output ---"
+# ---------------------------------------------------------------------------
+
+make_git 0; make_claude 0
+output=$(capture_hook)
+echo "$output" | grep -q "kyberforge cache updated" \
+  && pass "prints success message when both git pull and claude succeed" \
+  || fail "should print success message when both commands succeed"
+
+# ---------------------------------------------------------------------------
+echo ""
+echo "--- post-push: warnings on failure ---"
+# ---------------------------------------------------------------------------
+
+make_git 1; make_claude 0
+output=$(capture_hook)
+echo "$output" | grep -qi "failed to pull" \
+  && pass "warns when git pull fails" \
+  || fail "should warn when git pull fails"
+
+make_git 0; make_claude 1
+output=$(capture_hook)
+echo "$output" | grep -qi "failed" \
+  && pass "warns when claude plugin update fails" \
+  || fail "should warn when claude plugin update fails"
+
+# ---------------------------------------------------------------------------
+echo ""
+echo "--- post-push: claude not called when git pull fails ---"
+# ---------------------------------------------------------------------------
+
+CLAUDE_LOG="$FAKE_HOME/claude-was-called"
+make_git 1; make_claude 0 "$CLAUDE_LOG"
+run_hook
+if [[ ! -f "$CLAUDE_LOG" ]]; then
+  pass "claude not called when git pull fails"
+else
+  fail "claude should not be called when git pull fails"
+fi
+
+# ---------------------------------------------------------------------------
+echo ""
+echo "Results: $PASS passed, $FAIL failed"
+[[ $FAIL -eq 0 ]]