Add workspace symbol alias regression coverage

[luisalias007-cmyk]

Summary

• Adds a regression test that builds a temporary vault containing frontmatter aliases.
• Verifies workspace symbols include aliases in the full empty-query response.
• Verifies alias names are discoverable through workspace-symbol fuzzy search.

/claim #263

Verification

• cargo fmt --check
• cargo check --tests could not complete in this Windows environment because no MSVC linker (link.exe) is installed.
• Retried with stable-x86_64-pc-windows-gnullvm; it first required x86_64-w64-mingw32-clang, then using rust-lld reached dependency linking but failed on missing Windows system libraries (bcrypt, advapi32).