feat: add Cline runtime support via .clinerules (#1605)

Adds a .clinerules file at the repo root so Cline (VS Code AI extension)
understands GSD's architecture, coding standards, and workflow constraints.

Closes #1509

tests/cline-support.test.cjs

@@ -0,0 +1,33 @@
+const { test, describe } = require('node:test');
+const assert = require('node:assert');
+const fs = require('fs');
+const path = require('path');
+
+describe('Cline runtime support', () => {
+  test('.clinerules file exists at repo root', () => {
+    const p = path.join(__dirname, '..', '.clinerules');
+    assert.ok(fs.existsSync(p), '.clinerules should exist at repo root');
+  });
+
+  test('.clinerules references GSD workflow enforcement', () => {
+    const content = fs.readFileSync(path.join(__dirname, '..', '.clinerules'), 'utf-8');
+    assert.ok(
+      content.includes('gsd') || content.includes('GSD') || content.includes('workflow'),
+      '.clinerules should mention GSD workflows'
+    );
+  });
+
+  test('.clinerules includes coding standards', () => {
+    const content = fs.readFileSync(path.join(__dirname, '..', '.clinerules'), 'utf-8');
+    assert.ok(content.includes('CommonJS') || content.includes('require'),
+      '.clinerules should mention CommonJS standard');
+    assert.ok(content.includes('node:test') || content.includes('node:assert'),
+      '.clinerules should mention test framework');
+  });
+
+  test('.clinerules includes architecture overview', () => {
+    const content = fs.readFileSync(path.join(__dirname, '..', '.clinerules'), 'utf-8');
+    assert.ok(content.includes('bin/lib') || content.includes('workflows') || content.includes('agents'),
+      '.clinerules should describe project architecture');
+  });
+});