test(mcp): cover CLI index_repository name override

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What does this PR do?

Adds a regression test for #823 covering the index_repository name override when invoked through the CLI/supervised indexing path.

The test indexes a small temporary repository with a custom project name and verifies that:

• the index_repository response preserves the requested project name
• list_projects reports the custom name
• search_graph can query the indexed project by that custom name

This matches the maintainer-requested coverage for repo_path + name, ensuring the response and stored project identity agree instead of silently falling back to the path-derived project name.

Closes #823.

Checklist

• Every commit is signed off (git commit -s) — required, CI rejects unsigned commits (DCO, see CONTRIBUTING.md)
• Tests pass locally (make -f Makefile.cbm test)
• Lint passes locally (make -f Makefile.cbm lint-ci)
• New behavior is covered by a test (reproduce-first for bug fixes)