Pin pnpm version to 10.28.0

Using "latest" can lead to non-reproducible builds if a new version
introduces breaking changes.

#520 (comment)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: dahlia

mise.toml

@@ -2,7 +2,7 @@
 bun = "1.2.22"
 deno = "2.6.4"
 node = "22"
-"npm:pnpm" = "latest"
+"npm:pnpm" = "10.28.0"
 
 # Installation and setup
 [tasks.install]