Make BDD tests exit code gating in staging workflow

[Copilot]

The BDD tests in the staging workflow were previously only generating warnings when they failed, with a message indicating that failures were "expected". Since the tests now pass consistently, this PR updates the workflow to properly gate on BDD test failures.

Changes Made

Before:

• BDD test failures showed ⚠️ BDD tests failed (this is expected as step definitions are not yet implemented)
• Used separate bdd_exit_code variable that didn't affect the overall workflow result
• Comment indicated "don't fail on BDD tests for now"

After:

• BDD test failures now show ❌ BDD tests failed (no longer suggesting failures are expected)
• BDD test failures now properly set exit_code=1 to fail the entire workflow
• Removed the comment about not failing on BDD tests
• Simplified variable naming (bdd_result instead of bdd_exit_code)

Testing

The workflow logic was validated with test scenarios covering:

• BDD tests pass → workflow succeeds
• BDD tests fail → workflow fails
• Basic tests fail, BDD tests pass → workflow fails (maintains existing behavior)
• Both test types fail → workflow fails

The service cleanup and exit code handling remain unchanged, ensuring the staging service is properly stopped regardless of test outcomes.

Fixes #243.

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[github-actions]

🦙 MegaLinter status: ❌ ERROR

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
❌ ACTION	actionlint	5		6	0	0.07s
✅ BASH	bash-exec	1		0	0	0.0s
✅ BASH	shellcheck	1		0	0	0.04s
⚠️ BASH	shfmt	1		1	0	0.01s
❌ C	cppcheck	8		8	0	0.26s
❌ CPP	cppcheck	8		8	0	0.27s
✅ JSON	npm-package-json-lint	yes		no	no	0.37s
✅ JSON	v8r	12		0	0	8.01s
❌ MARKDOWN	markdown-link-check	736		213	0	35.31s
✅ REPOSITORY	gitleaks	yes		no	no	12.81s
✅ REPOSITORY	git_diff	yes		no	no	0.33s
✅ REPOSITORY	grype	yes		no	no	36.23s
✅ REPOSITORY	secretlint	yes		no	no	43.14s
✅ REPOSITORY	syft	yes		no	no	1.96s
✅ REPOSITORY	trivy-sbom	yes		no	no	3.24s
✅ REPOSITORY	trufflehog	yes		no	no	4.65s
✅ XML	xmllint	1		0	0	192.14s
✅ YAML	v8r	13		0	0	7.11s

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