refactor: move setup scripts out of src/ to reduce build token count

Setup scripts are standalone CLI tools run via tsx with no runtime
imports from the main app. Moving them out of src/ excludes them from
the tsc build output and reduces the compiled bundle size.

- git mv src/setup/ setup/
- Fix imports to use ../src/logger.js and ../src/config.js
- Update package.json, vitest.config.ts, SKILL.md references
- Fix platform tests to be cross-platform (macOS + Linux)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

setup/status.ts

@@ -0,0 +1,16 @@
+/**
+ * Structured status block output for setup steps.
+ * Each step emits a block that the SKILL.md LLM can parse.
+ */
+
+export function emitStatus(
+  step: string,
+  fields: Record<string, string | number | boolean>,
+): void {
+  const lines = [`=== NANOCLAW SETUP: ${step} ===`];
+  for (const [key, value] of Object.entries(fields)) {
+    lines.push(`${key}: ${value}`);
+  }
+  lines.push('=== END ===');
+  console.log(lines.join('\n'));
+}