fix(setup): link lib/ beside bin/ at all five host-install sites

bin/ scripts import shared modules via ../lib (gstack-learnings-log →
lib/jsonl-store.ts is the reported case), so any runtime root that
exposes bin/ without lib/ breaks 13 bin/ commands — learnings-log,
decision-log, telemetry and friends fail with "Cannot find module
.../lib/jsonl-store.ts" on every non-Claude install, silently from the
skills' perspective.

All five host-install sites now carry lib/ next to bin/, each through
the existing _link_or_copy helper (never raw ln — the static invariant
in test/setup-windows-fallback.test.ts enforces this):

- .agents sidecar (create_agents_sidecar asset loop)
- Codex runtime root (create_codex_runtime_root)
- Factory runtime root (create_factory_runtime_root)
- OpenCode runtime root (create_opencode_runtime_root)
- Kiro install block

New test/setup-runtime-lib-command.test.ts executes the real setup shell
for each root in a sandbox (both the symlink branch and the Windows copy
branch of _link_or_copy) and runs gstack-learnings-log end-to-end from
the installed root, asserting the learning lands in
~/.gstack/projects/<slug>/learnings.jsonl — plus a negative control
proving a bin-without-lib root fails exactly the way the bug report did.
gen-skill-docs.test.ts's setup-validation block pins the lib link at
every site. Cross-checked against PRs #2433, #2410 and #2198: all three
cover subsets of these sites; nothing they fix is missing here.

Contributed by @fedster99 (PR #2262); overlapping fixes by @gregario, @lsendel and @netkurt.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

setup

@@ -758,8 +758,9 @@ create_agents_sidecar() {
   local agents_gstack="$repo_root/.agents/skills/gstack"
   mkdir -p "$agents_gstack"
 
-  # Sidecar directories that skills reference at runtime
-  for asset in bin browse review qa; do
+  # Sidecar directories that skills reference at runtime. bin scripts import
+  # shared modules via ../lib, so bin and lib must always travel together.
+  for asset in bin lib browse review qa; do
     local src="$SOURCE_GSTACK_DIR/$asset"
     local dst="$agents_gstack/$asset"
     if [ -d "$src" ] || [ -f "$src" ]; then
@@ -806,6 +807,9 @@ create_codex_runtime_root() {
   if [ -d "$gstack_dir/bin" ]; then
     _link_or_copy "$gstack_dir/bin" "$codex_gstack/bin"
   fi
+  if [ -d "$gstack_dir/lib" ]; then
+    _link_or_copy "$gstack_dir/lib" "$codex_gstack/lib"
+  fi
   if [ -d "$gstack_dir/browse/dist" ]; then
     _link_or_copy "$gstack_dir/browse/dist" "$codex_gstack/browse/dist"
   fi
@@ -846,6 +850,9 @@ create_factory_runtime_root() {
   if [ -d "$gstack_dir/bin" ]; then
     _link_or_copy "$gstack_dir/bin" "$factory_gstack/bin"
   fi
+  if [ -d "$gstack_dir/lib" ]; then
+    _link_or_copy "$gstack_dir/lib" "$factory_gstack/lib"
+  fi
   if [ -d "$gstack_dir/browse/dist" ]; then
     _link_or_copy "$gstack_dir/browse/dist" "$factory_gstack/browse/dist"
   fi
@@ -884,6 +891,9 @@ create_opencode_runtime_root() {
   if [ -d "$gstack_dir/bin" ]; then
     _link_or_copy "$gstack_dir/bin" "$opencode_gstack/bin"
   fi
+  if [ -d "$gstack_dir/lib" ]; then
+    _link_or_copy "$gstack_dir/lib" "$opencode_gstack/lib"
+  fi
   if [ -d "$gstack_dir/browse/dist" ]; then
     _link_or_copy "$gstack_dir/browse/dist" "$opencode_gstack/browse/dist"
   fi
@@ -1125,6 +1135,7 @@ if [ "$INSTALL_KIRO" -eq 1 ]; then
   [ -L "$KIRO_GSTACK" ] && rm -f "$KIRO_GSTACK"
   mkdir -p "$KIRO_GSTACK" "$KIRO_GSTACK/browse" "$KIRO_GSTACK/gstack-upgrade" "$KIRO_GSTACK/review"
   _link_or_copy "$SOURCE_GSTACK_DIR/bin" "$KIRO_GSTACK/bin"
+  _link_or_copy "$SOURCE_GSTACK_DIR/lib" "$KIRO_GSTACK/lib"
   _link_or_copy "$SOURCE_GSTACK_DIR/browse/dist" "$KIRO_GSTACK/browse/dist"
   _link_or_copy "$SOURCE_GSTACK_DIR/browse/bin" "$KIRO_GSTACK/browse/bin"
   # ETHOS.md — referenced by "Search Before Building" in all skill preambles