fix: Codex sidecar paths + setup installs generated skills

Two bugs found by Codex adversarial review:

1. Sidecar path mismatch: generated Codex skills referenced
   .agents/skills/gstack-review/checklist.md but setup creates
   sidecars at .agents/skills/gstack/review/. Fixed path rewriter
   to emit .agents/skills/gstack/review/ (matching setup layout).

2. Setup installed Claude-format source dirs for Codex global
   install instead of the generated Codex-format skills. Split
   link_skill_dirs into link_claude_skill_dirs (source dirs for
   Claude) and link_codex_skill_dirs (generated .agents/skills/
   gstack-* dirs for Codex).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

setup

@@ -91,8 +91,8 @@ fi
 # 3. Ensure ~/.gstack global state directory exists
 mkdir -p "$HOME/.gstack/projects"
 
-# ─── Helper: link skill subdirectories into a skills parent directory ──
-link_skill_dirs() {
+# ─── Helper: link Claude skill subdirectories into a skills parent directory ──
+link_claude_skill_dirs() {
   local gstack_dir="$1"
   local skills_dir="$2"
   local linked=()
@@ -114,6 +114,36 @@ link_skill_dirs() {
   fi
 }
 
+# ─── Helper: link generated Codex skills into a skills parent directory ──
+# Installs from .agents/skills/gstack-* (the generated Codex-format skills)
+# instead of source dirs (which have Claude paths).
+link_codex_skill_dirs() {
+  local gstack_dir="$1"
+  local skills_dir="$2"
+  local agents_dir="$gstack_dir/.agents/skills"
+  local linked=()
+
+  if [ ! -d "$agents_dir" ]; then
+    echo "  warning: no .agents/skills/ directory found — run 'bun run build' first" >&2
+    return 1
+  fi
+
+  for skill_dir in "$agents_dir"/gstack*/; do
+    if [ -f "$skill_dir/SKILL.md" ]; then
+      skill_name="$(basename "$skill_dir")"
+      target="$skills_dir/$skill_name"
+      # Create or update symlink
+      if [ -L "$target" ] || [ ! -e "$target" ]; then
+        ln -snf "$skill_dir" "$target"
+        linked+=("$skill_name")
+      fi
+    fi
+  done
+  if [ ${#linked[@]} -gt 0 ]; then
+    echo "  linked skills: ${linked[*]}"
+  fi
+}
+
 # ─── Helper: create .agents/skills/gstack/ sidecar symlinks ──────────
 # Codex/Gemini/Cursor read skills from .agents/skills/. We link runtime
 # assets (bin/, browse/dist/, review/, qa/, etc.) so skill templates can
@@ -139,7 +169,7 @@ create_agents_sidecar() {
 SKILLS_BASENAME="$(basename "$SKILLS_DIR")"
 if [ "$INSTALL_CLAUDE" -eq 1 ]; then
   if [ "$SKILLS_BASENAME" = "skills" ]; then
-    link_skill_dirs "$GSTACK_DIR" "$SKILLS_DIR"
+    link_claude_skill_dirs "$GSTACK_DIR" "$SKILLS_DIR"
     echo "gstack ready (claude)."
     echo "  browse: $BROWSE_BIN"
   else
@@ -155,11 +185,12 @@ if [ "$INSTALL_CODEX" -eq 1 ]; then
   CODEX_GSTACK="$CODEX_SKILLS/gstack"
   mkdir -p "$CODEX_SKILLS"
 
-  # Symlink or copy gstack into ~/.codex/skills/gstack
+  # Symlink gstack source for runtime assets (bin/, browse/dist/)
   if [ -L "$CODEX_GSTACK" ] || [ ! -e "$CODEX_GSTACK" ]; then
     ln -snf "$GSTACK_DIR" "$CODEX_GSTACK"
   fi
-  link_skill_dirs "$GSTACK_DIR" "$CODEX_SKILLS"
+  # Install generated Codex-format skills (not Claude source dirs)
+  link_codex_skill_dirs "$GSTACK_DIR" "$CODEX_SKILLS"
 
   echo "gstack ready (codex)."
   echo "  browse: $BROWSE_BIN"