Remove unused hasInternalPrefix function causing lint failure

[Copilot]

The lint-go workflow was failing due to an unused helper function hasInternalPrefix in pkg/workflow/compiler_orchestrator_test.go. This function was added in commit cb57a14 during validation error refactoring but never called.

Changes:

• Removed unused hasInternalPrefix function (5 lines) from test file

// Removed:
func hasInternalPrefix(key string) bool {
	return len(key) > 2 && key[0] == '_' && key[1] == '_'
}

The golangci-lint unused checker now passes without errors.

Original prompt

Fix the failing GitHub Actions workflow lint-go
Analyze the workflow logs, identify the root cause of the failure, and implement a fix.
Format, lint, recompile
Job ID: 60843569956
Job URL: https://github.com/githubnext/gh-aw/actions/runs/21156947459/job/60843569956

Custom agent used: ci-cleaner
Tidies up the repository CI state by formatting sources, running linters, fixing issues, running tests, and recompiling workflows

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