test: increase test coverage for loaders.ts file rendering

[ulises-jeremias]

Context

Four file loaders (copyLoader, appendLoader, copyTemplate, appendTemplate) lack comprehensive tests.

Task

Test: happy paths, missing variables, edge cases (empty, binary, large files), undefined/null/special chars.

Files to modify

• packages/create-node-app-core/tests/ — add loaders test file

Verification

• 80% branch coverage for all loaders

Steps

1. Test: happy paths, missing variables, edge cases (empty, binary, large files), undefined/null/special chars.
2. packages/create-node-app-core/tests/ — add loaders test file

3. 80% branch coverage for all loaders

Acceptance criteria

• >80% branch coverage for all loaders

Files

• packages/create-node-app-core/tests/ — add loaders test file

Verification

• 80% branch coverage for all loaders

How to verify

• 80% branch coverage for all loaders

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Original issue text

Description

Four file loaders (copyLoader, appendLoader, copyTemplate, appendTemplate) lack comprehensive tests.

Task

Test: happy paths, missing variables, edge cases (empty, binary, large files), undefined/null/special chars.

Files to modify

• packages/create-node-app-core/tests/ — add loaders test file

Verification

• 80% branch coverage for all loaders