fix(setup): alias skills install as rewritten copies, never symlinks

The two back-compat alias dirs — _gstack-command (root router) and
connect-chrome (→ open-gstack-browser) — symlinked the canonical SKILL.md
verbatim, so each alias re-served the canonical frontmatter name:. Claude
Code keys skills on that name and requires global uniqueness: the
connect-chrome duplicate silently shadowed /open-gstack-browser (whichever
readdir returned first won), and the _gstack-command duplicate could drop
the ENTIRE personal-skills set — every /gstack command vanished until the
user hand-deleted the alias dirs, and the next setup re-broke it.

Fix: copy-then-rewrite. A shared _install_alias_skill_md helper reads the
SOURCE SKILL.md and writes a fresh copy with name: rewritten to the alias
dir's own name (_gstack-command / connect-chrome / gstack-connect-chrome).
sed never edits in place: on Unix the old install was a symlink into the
repo, and an in-place rewrite through it would have corrupted the generated
source (eng review E2). bin/gstack-relink gets the same treatment for its
root-alias helper, and its discovery loop now skips symlinked source dirs
so the connect-chrome repo symlink can't re-mint the duplicate.

Tests assert: installed aliases are NOT symlinks, carry their own unique
names, all installed frontmatter names are globally unique, re-runs refresh
cleanly, legacy symlinked aliases are replaced not written through, and the
source files stay byte-intact.

Fixes #2511
Fixes #2201

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

test/relink.test.ts

@@ -215,9 +215,15 @@ describe('gstack-relink (#578)', () => {
     const aliasSkill = path.join(aliasDir, 'SKILL.md');
     expect(fs.lstatSync(aliasDir).isDirectory()).toBe(true);
     expect(fs.lstatSync(aliasDir).isSymbolicLink()).toBe(false);
-    expect(fs.lstatSync(aliasSkill).isSymbolicLink()).toBe(true);
-    expect(fs.readlinkSync(aliasSkill)).toBe(path.join(installDir, 'SKILL.md'));
-    expect(fs.readFileSync(aliasSkill, 'utf-8')).toContain('name: gstack');
+    // #2511: the alias is a rewritten COPY, never a symlink. A symlinked
+    // alias re-serves the canonical `name: gstack`; Claude Code refuses
+    // duplicate skill names and drops the entire personal-skills set.
+    expect(fs.lstatSync(aliasSkill).isSymbolicLink()).toBe(false);
+    const aliasContent = fs.readFileSync(aliasSkill, 'utf-8');
+    expect(aliasContent).toContain('name: _gstack-command');
+    expect(aliasContent).not.toContain('name: gstack\n');
+    // The rewrite happened on the COPY: the canonical source keeps its name.
+    expect(fs.readFileSync(path.join(installDir, 'SKILL.md'), 'utf-8')).toContain('name: gstack');
 
     run(`${path.join(installDir, 'bin', 'gstack-config')} set skill_prefix true`, {
       GSTACK_INSTALL_DIR: installDir,
@@ -226,6 +232,40 @@ describe('gstack-relink (#578)', () => {
     expect(fs.existsSync(aliasSkill)).toBe(true);
   });
 
+  // #2201: connect-chrome ships as a dir SYMLINK to open-gstack-browser. The
+  // discovery loop used to link it under its own basename while its SKILL.md
+  // carried `name: open-gstack-browser` — a duplicate name that silently
+  // shadows the real skill (readdir-order roulette). Symlinked source dirs
+  // must be skipped; setup owns the rewritten-copy alias.
+  test('symlinked skill dirs are skipped, so no duplicate frontmatter names (#2201)', () => {
+    setupMockInstall(['open-gstack-browser', 'qa']);
+    fs.symlinkSync(
+      path.join(installDir, 'open-gstack-browser'),
+      path.join(installDir, 'connect-chrome'),
+    );
+    run(`${path.join(installDir, 'bin', 'gstack-config')} set skill_prefix false`, {
+      GSTACK_INSTALL_DIR: installDir,
+      GSTACK_SKILLS_DIR: skillsDir,
+    });
+    run(`${path.join(installDir, 'bin', 'gstack-relink')}`, {
+      GSTACK_INSTALL_DIR: installDir,
+      GSTACK_SKILLS_DIR: skillsDir,
+    });
+
+    expect(fs.existsSync(path.join(skillsDir, 'open-gstack-browser'))).toBe(true);
+    expect(fs.existsSync(path.join(skillsDir, 'connect-chrome'))).toBe(false);
+
+    // No two installed SKILL.md files may share a frontmatter name.
+    const names: string[] = [];
+    for (const entry of fs.readdirSync(skillsDir)) {
+      const skillMd = path.join(skillsDir, entry, 'SKILL.md');
+      if (!fs.existsSync(skillMd)) continue;
+      const m = fs.readFileSync(skillMd, 'utf-8').match(/^name:\s*(\S+)/m);
+      if (m) names.push(m[1]);
+    }
+    expect(new Set(names).size).toBe(names.length);
+  });
+
   // FIRST INSTALL: --no-prefix must create ONLY flat names, zero gstack-* pollution
   test('first install --no-prefix: only flat names exist, zero gstack-* entries', () => {
     setupMockInstall(['qa', 'ship', 'review', 'plan-ceo-review', 'gstack-upgrade']);