spec-spine: Hook for Claude Code

{
  "SessionStart": [
    {
      "matcher": "startup|resume|clear|compact",
      "hooks": [
        {
          "type": "command",
          "command": "cd \"${CLAUDE_PROJECT_DIR:-.}\" 2>/dev/null || exit 0\n[ -d specs ] || exit 0\n# Resolve the spec-spine binary for the repository this hook acts on:\n# $SPEC_SPINE_BIN, then that repository's own release build, then PATH. A repo\n# that builds its own binary must be governed by the one it builds; the PATH\n# fallback keeps an adopter on the published CLI working (spec 051).\nspec_spine_bin() {\n  if [ -n \"${SPEC_SPINE_BIN:-}\" ] && [ -x \"${SPEC_SPINE_BIN}\" ]; then echo \"${SPEC_SPINE_BIN}\"; return 0; fi\n  if [ -x \"$1/target/release/spec-spine\" ]; then echo \"$1/target/release/spec-spine\"; return 0; fi\n  command -v spec-spine 2>/dev/null\n}\nif sc=$(spec_spine_bin \"${CLAUDE_PROJECT_DIR:-.}\") && [ -n \"$sc\" ]; then\n  # Spec 063: establish the binary understands the flag BEFORE reading its exit\n  # code. A binary predating `compile --check` rejects the unknown flag, and\n  # clap spent exit 2 on that, which is the code this tool spends on staleness.\n  # A session told its shards are stale when they are not will regenerate and\n  # commit artifacts that were already correct. `--version` is answered by every\n  # binary ever released, so asking is safe against any version.\n  ver=$(\"$sc\" --version 2>/dev/null | awk '{print $NF}')\n  if ! \"$sc\" compile --check --help >/dev/null 2>&1; then\n    reg=\"spec-spine ${ver:-?} predates \\`compile --check\\`, rebuild or reinstall (see /setup)\"\n    idx=\"$reg\"\n  else\n  # Read-only: `compile --check` compares the committed shards to the corpus\n  # without writing (spec 031). A bare `compile` would repair a stale\n  # committed tree as a side effect of reading it, hiding the defect.\n  \"$sc\" compile --check >/dev/null 2>&1; c=$?\n  case $c in\n    0) reg='fresh' ;;\n    2) reg='STALE, run spec-spine compile and commit the shards' ;;\n    1) reg='INVALID,