Nightly build 2025.03.07

What's Changed

Toolchain and implementation changes 🛠️

• Add a test that should catch checking poisoned names when extending a class by @bricknerb in #5071
• Support mangling imported C++ functions using Clang's MangleContext by @bricknerb in #5062
• Continue: emit function definitions for specifics. by @alinas in #5068
• Find impl witnesses in facets by @josh11b in #5060
• Handle impl with bad interface on import by @josh11b in #5051
• Add support for var patterns by @geoffromer in #5069
• Fix non-instance compound member access by @josh11b in #5059

Full Changelog: v0.0.0-0.nightly.2025.03.06...v0.0.0-0.nightly.2025.03.07