This PR adds declaration names to leanchecker error messages to make
debugging easier when the kernel rejects a declaration.
Previously, leanchecker would only show the kernel error without
identifying which declaration failed:
```
uncaught exception: (kernel) type checker does not support loose bound variables
```
Now it includes the declaration name:
```
uncaught exception: while replaying declaration 'myDecl':
(kernel) type checker does not support loose bound variables
```
Fixes: #11937
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: nomeata <148037+nomeata@users.noreply.github.com>
This PR makes the external checker lean4checker available as the
existing `leanchecker` binary already known to elan, allowing for
out-of-the-box access to it.
---------
Co-authored-by: Kim Morrison <kim@tqft.net>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
