[BUG] loong64 deb package copies the binary to the wrong path

[equationzhao]

Describe the bug
The deb recipe builds the loong64 package with an incorrect copy destination. Other architectures copy the binary to usr/local/bin/g, but the loong64 branch copies it into usr.

This can produce a loong64 .deb package without the expected /usr/local/bin/g executable.

To Reproduce

1. Build release artifacts including deb packages:

   just build
   just deb

2. Inspect the loong64 package contents.
3. The binary path differs from other architectures.

Screenshots
Not applicable.

Info (please complete the following information):

• OS: release packaging
• Version: v0.31.2

Additional context
Relevant line in justfile:

cp build/g-linux-loong64 build/g_{{latest}}_loong64/usr

It likely should mirror the other architectures and copy to:

build/g_{{latest}}_loong64/usr/local/bin/g