chore: remove, just, from, .tool-versions

Batch Justfile audit: standardised naming (lowercase→Justfile),
fixed parse errors, removed useless build-riscv from non-Rust repos,
added missing assail recipe, and fixed code quality issues.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.tool-versions

@@ -5,5 +5,3 @@
 # Primary runtime
 deno 2.1.4
 
-# Build tools
-just 1.36.0