C1: skillify finds the browse SDK under its own host's install root

The template hardcoded ~/.claude/skills/gstack for the canonical
browse-client.ts, so external hosts read another host's install or nothing.
A new INSTALLED_ROOT resolver (sibling of INSTALLED_BIN_DIR) names the host's
global root, or the per-install root when setup renders for one.

scripts/resolvers/index.ts

@@ -143,6 +143,7 @@ export const RESOLVERS: Record<string, ResolverFn> = {
   // Literal bin dir for skills that skip the shared preamble, where
   // $GSTACK_BIN is never set (#2906): the per-install root when rendering for
   // one, else the host's default global root.
+  INSTALLED_ROOT: (ctx) => ctx.installRoot ? ctx.installRoot.replace(/\/+$/, '') : `~/${getHostConfig(ctx.host).globalRoot}`,
   INSTALLED_BIN_DIR: (ctx) => ctx.installRoot ? `${ctx.installRoot.replace(/\/+$/, '')}/bin` : `~/${getHostConfig(ctx.host).globalRoot}/bin`,
   FOREGROUND_DISPATCH_NOTE: () => FOREGROUND_DISPATCH_NOTE,
   GBRAIN_CONTEXT_LOAD: generateGBrainContextLoad,

skillify/SKILL.md.tmpl

@@ -220,7 +220,7 @@ Resolve the gstack install dir. Two reliable signals (in order):
    `$B skill list` (the `bundled` row). The skill dir is
    `<gstack-install>/browser-skills/hackernews-frontpage/`, so the install
    dir is two `dirname` calls above its `_lib/browse-client.ts`.
-2. The active gstack skills install at `~/.claude/skills/gstack/`. Read
+2. The active gstack skills install at `{{INSTALLED_ROOT}}/`. Read
    the symlink target if it's a symlink, otherwise use the path directly.
 
 Example (run as Bun, not bash, to avoid shell-redirect parsing issues):
@@ -232,7 +232,7 @@ import * as path from 'path';
 
 function resolveSdkPath(): string {
   const candidates = [
-    path.join(os.homedir(), '.claude', 'skills', 'gstack', 'browse', 'src', 'browse-client.ts'),
+    '{{INSTALLED_ROOT}}/browse/src/browse-client.ts'.replace(/^~(?=\/)/, os.homedir()),
     // Add other install-dir candidates if your environment differs.
   ];
   for (const c of candidates) {

test/skillify-host-paths.test.ts

@@ -0,0 +1,28 @@
+/**
+ * /skillify resolved the browse SDK at ~/.claude/skills/gstack on every host,
+ * so on Codex and the other external hosts it read another host's install (or
+ * nothing). The install root now comes from the host config (INSTALLED_ROOT).
+ */
+import { afterAll, beforeAll, describe, expect, test } from 'bun:test';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { ALL_HOST_CONFIGS } from '../hosts';
+import { runGeneration } from '../scripts/gen-skill-docs';
+
+const out = fs.mkdtempSync(path.join(os.tmpdir(), 'gstack-skillify-paths-'));
+beforeAll(async () => { expect((await runGeneration({ host: 'all', outputRoot: out })).exitCode).toBe(0); });
+afterAll(() => fs.rmSync(out, { recursive: true, force: true }));
+
+describe('skillify resolves the browse SDK from its own host install', () => {
+  for (const host of ALL_HOST_CONFIGS) {
+    test(host.name, () => {
+      const file = host.name === 'claude' ? path.join(out, 'skillify/SKILL.md') : path.join(out, host.hostSubdir, 'skills/gstack-skillify/SKILL.md');
+      if (!fs.existsSync(file)) return;
+      const text = fs.readFileSync(file, 'utf8');
+      const sdk = text.split('\n').filter(l => l.includes('browse-client.ts') && /homedir|replace/.test(l));
+      expect(sdk).toEqual([`    '~/${host.globalRoot}/browse/src/browse-client.ts'.replace(/^~(?=\\/)/, os.homedir()),`]);
+      expect(text).toContain(`The active gstack skills install at \`~/${host.globalRoot}/\``);
+    });
+  }
+});