Fix the duplicate-name regression test that passes even when duplicates are stored

[kwannoel]

Summary

• src-tauri/tests/integration.rs:166 says it verifies the invariant that project names must be unique.
• The test then saves two projects with the same name and only asserts count >= 1 at src-tauri/tests/integration.rs:211.

That assertion stays green even when duplicate-name handling regresses, so the test does not protect the invariant its name and comments claim to cover. Remediation: move the check to the command layer that enforces uniqueness, or rewrite the test so it fails when duplicate names are actually admitted.

Maintainer Metadata

• Fingerprint: coverage|duplicate|false|integration|missing|name|positive|test|tests
• Symptom Type: missing coverage
• Affected Files: src-tauri/tests/integration.rs
• Keywords: duplicate_project_name, integration_test, false_positive, coverage