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>

test/gen-skill-docs.test.ts

@@ -2406,6 +2406,7 @@ describe('setup script validation', () => {
     expect(setupContent).toContain('kiro-cli');
     expect(setupContent).toContain('KIRO_SKILLS=');
     expect(setupContent).toContain('~/.kiro/skills/gstack');
+    expect(setupContent).toContain('$KIRO_GSTACK/lib');
   });
 
   test('setup supports --host opencode with install section and OpenCode skill path vars', () => {
@@ -2421,14 +2422,16 @@ describe('setup script validation', () => {
     expect(setupContent).toContain('qa/templates');
     expect(setupContent).toContain('qa/references');
     expect(setupContent).toContain('dx-hall-of-fame.md');
+    expect(setupContent).toContain('$opencode_gstack/lib');
   });
 
   test('create_agents_sidecar links runtime assets', () => {
-    // Sidecar must link bin, browse, review, qa
+    // Sidecar must link bin with its shared lib modules, plus browse, review, qa
     const fnStart = setupContent.indexOf('create_agents_sidecar()');
     const fnEnd = setupContent.indexOf('}', setupContent.indexOf('done', fnStart));
     const fnBody = setupContent.slice(fnStart, fnEnd);
     expect(fnBody).toContain('bin');
+    expect(fnBody).toContain('lib');
     expect(fnBody).toContain('browse');
     expect(fnBody).toContain('review');
     expect(fnBody).toContain('qa');
@@ -2439,6 +2442,7 @@ describe('setup script validation', () => {
     const fnEnd = setupContent.indexOf('}', setupContent.indexOf('done', setupContent.indexOf('review/', fnStart)));
     const fnBody = setupContent.slice(fnStart, fnEnd);
     expect(fnBody).toContain('gstack/SKILL.md');
+    expect(fnBody).toContain('$codex_gstack/lib');
     expect(fnBody).toContain('browse/dist');
     expect(fnBody).toContain('browse/bin');
     expect(fnBody).toContain('gstack-upgrade/SKILL.md');
@@ -2450,6 +2454,14 @@ describe('setup script validation', () => {
     expect(fnBody).not.toContain('_link_or_copy "$gstack_dir" "$codex_gstack"');
   });
 
+  test('create_factory_runtime_root links shared lib modules beside bin', () => {
+    const fnStart = setupContent.indexOf('create_factory_runtime_root()');
+    const fnEnd = setupContent.indexOf('create_opencode_runtime_root()', fnStart);
+    const fnBody = setupContent.slice(fnStart, fnEnd);
+    expect(fnBody).toContain('$factory_gstack/bin');
+    expect(fnBody).toContain('$factory_gstack/lib');
+  });
+
   test('direct Codex installs are migrated out of ~/.codex/skills/gstack', () => {
     expect(setupContent).toContain('migrate_direct_codex_install');
     expect(setupContent).toContain('$HOME/.gstack/repos/gstack');