Add droid and cursor sync targets, extract shared path helpers

- Add sync --target droid (skills to ~/.factory/skills/)
- Add sync --target cursor (skills + MCP to .cursor/)
- Extract expandHome/resolveTargetHome to src/utils/resolve-home.ts
- Remove duplicated path helpers from convert.ts and install.ts
- Bump version to 0.6.0

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

src/utils/resolve-home.ts

@@ -0,0 +1,17 @@
+import os from "os"
+import path from "path"
+
+export function expandHome(value: string): string {
+  if (value === "~") return os.homedir()
+  if (value.startsWith(`~${path.sep}`)) {
+    return path.join(os.homedir(), value.slice(2))
+  }
+  return value
+}
+
+export function resolveTargetHome(value: unknown, defaultPath: string): string {
+  if (!value) return defaultPath
+  const raw = String(value).trim()
+  if (!raw) return defaultPath
+  return path.resolve(expandHome(raw))
+}