feat(gstack-config): gbrain-refresh renders brain-aware blocks into the install

Extends gbrain-refresh to render the :user variant into the global install
(~/.claude/skills/gstack) so every project's Claude sessions get brain-aware
blocks, not just the gstack dev workspace. Guarded against mutating the wrong
directory: the target must exist, not be a symlink (a symlinked install points
at a dev worktree), and look like a real gstack clone (VERSION + package.json).
Idempotent and self-documenting. CLAUDE.md's deploy section now notes that
'git reset --hard' reverts the blocks and to re-run gbrain-refresh.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

test/gbrain-refresh-install-render.test.ts

@@ -0,0 +1,60 @@
+import { describe, test, expect } from 'bun:test';
+import * as path from 'path';
+import * as fs from 'fs';
+
+// Static tripwires for the C (machine-wide) render in `gstack-config
+// gbrain-refresh`. The render mutates the shared global install, so the guards
+// that stop it from touching the wrong directory are load-bearing — these fail
+// CI if any guard is dropped.
+const ROOT = path.resolve(import.meta.dir, '..');
+const SRC = fs.readFileSync(path.join(ROOT, 'bin', 'gstack-config'), 'utf-8');
+
+// Pull out just the gbrain-refresh `ok)` branch so assertions can't be
+// satisfied by unrelated text elsewhere in the file.
+function okBranch(): string {
+  const start = SRC.indexOf('gbrain-refresh)');
+  const ok = SRC.indexOf('ok)', start);
+  const end = SRC.indexOf(';;', ok);
+  if (start < 0 || ok < 0 || end < 0) throw new Error('Could not locate gbrain-refresh ok) branch');
+  return SRC.slice(ok, end);
+}
+
+describe('gstack-config gbrain-refresh: machine-wide render guards', () => {
+  const branch = okBranch();
+
+  test('targets the global install', () => {
+    expect(branch).toContain('$HOME/.claude/skills/gstack');
+  });
+
+  test('refuses a symlinked install (would dirty a dev worktree)', () => {
+    expect(branch).toMatch(/\[ -L "\$INSTALL_DIR" \]/);
+  });
+
+  test('verifies it is a real gstack clone before mutating it', () => {
+    expect(branch).toContain('$INSTALL_DIR/VERSION');
+    expect(branch).toContain('$INSTALL_DIR/package.json');
+  });
+
+  test('requires bun on PATH', () => {
+    expect(branch).toContain('command -v bun');
+  });
+
+  test('renders the :user variant in place into the install', () => {
+    expect(branch).toContain('gen:skill-docs:user --host claude');
+  });
+
+  test('is self-documenting about the reset --hard / re-run cycle', () => {
+    expect(branch).toContain('reset --hard');
+    expect(branch).toContain('gbrain-refresh');
+  });
+});
+
+describe('CLAUDE.md: deploy section documents the re-run', () => {
+  test('notes re-running gbrain-refresh after reset --hard', () => {
+    const claudeMd = fs.readFileSync(path.join(ROOT, 'CLAUDE.md'), 'utf-8');
+    const idx = claudeMd.indexOf('## Deploying to the active skill');
+    expect(idx).toBeGreaterThan(-1);
+    const section = claudeMd.slice(idx, idx + 1200);
+    expect(section).toContain('gbrain-refresh');
+  });
+});