feat(02-02): implement buildRcloneConf pure function

- Maps BackendType to rclone INI type strings via RCLONE_TYPE_MAP
- s3-compatible correctly maps to type = s3 (not s3-compatible)
- Omits empty param values from output (no 'sas_url =' when blank)
- Throws on null backendType or empty remote name
- All 17 rclone-conf.test.ts assertions pass GREEN

src/generators/rclone-conf.ts

@@ -0,0 +1,31 @@
+// src/generators/rclone-conf.ts
+// Pure function: converts WizardState into a valid rclone.conf INI string.
+// SECURITY: No logging — state contains credentials. Do NOT add console.log here.
+
+import type { WizardState } from '../store/types';
+
+// Maps our BackendType to rclone's internal type string.
+// IMPORTANT: s3-compatible uses 'type = s3' — rclone does not recognize 's3-compatible' as a type.
+// S3-compatible backends are differentiated by provider = Other in params.
+const RCLONE_TYPE_MAP: Record<string, string> = {
+  azureblob: 'azureblob',
+  s3: 's3',
+  's3-compatible': 's3',
+};
+
+export function buildRcloneConf(state: WizardState): string {
+  const { name, backendType, params } = state.remote;
+  if (!backendType) throw new Error('buildRcloneConf: backendType is required');
+  if (!name) throw new Error('buildRcloneConf: remote name is required');
+
+  const rcloneType = RCLONE_TYPE_MAP[backendType];
+  const lines: string[] = [`[${name}]`, `type = ${rcloneType}`];
+
+  for (const [key, value] of Object.entries(params)) {
+    if (value !== '') {
+      lines.push(`${key} = ${value}`);
+    }
+  }
+
+  return lines.join('\n') + '\n';
+}