fix(fs): add comprehensive error handling for readJson operations

Improve error messages for JSON file reading failures in both async and sync versions:
- ENOENT: File not found with guidance on creating the file
- EACCES/EPERM: Permission denied with access guidance

Users now get actionable guidance instead of generic ENOENT/EACCES errors.

Also fixes formatting in dlx-package.ts for long condition.

Author: jdalton

src/dlx-package.ts

@@ -200,7 +200,11 @@ async function ensurePackageInstalled(
             { cause: e },
           )
         }
-        if (code === 'ENOTFOUND' || code === 'ETIMEDOUT' || code === 'EAI_AGAIN') {
+        if (
+          code === 'ENOTFOUND' ||
+          code === 'ETIMEDOUT' ||
+          code === 'EAI_AGAIN'
+        ) {
           throw new Error(
             `Network error installing ${packageSpec}\n` +
               'Check your internet connection and try again.',

src/fs.ts

@@ -984,6 +984,21 @@ export async function readJson(
     })
   } catch (e) {
     if (shouldThrow) {
+      const code = (e as NodeJS.ErrnoException).code
+      if (code === 'ENOENT') {
+        throw new Error(
+          `JSON file not found: ${filepath}\n` +
+            'Ensure the file exists or create it with the expected structure.',
+          { cause: e },
+        )
+      }
+      if (code === 'EACCES' || code === 'EPERM') {
+        throw new Error(
+          `Permission denied reading JSON file: ${filepath}\n` +
+            'Check file permissions or run with appropriate access.',
+          { cause: e },
+        )
+      }
       throw e
     }
     return undefined
@@ -1046,6 +1061,21 @@ export function readJsonSync(
     })
   } catch (e) {
     if (shouldThrow) {
+      const code = (e as NodeJS.ErrnoException).code
+      if (code === 'ENOENT') {
+        throw new Error(
+          `JSON file not found: ${filepath}\n` +
+            'Ensure the file exists or create it with the expected structure.',
+          { cause: e },
+        )
+      }
+      if (code === 'EACCES' || code === 'EPERM') {
+        throw new Error(
+          `Permission denied reading JSON file: ${filepath}\n` +
+            'Check file permissions or run with appropriate access.',
+          { cause: e },
+        )
+      }
       throw e
     }
     return undefined