Pin Bun version to 1.2.22

Bun 1.2.23 introduced a regression causing false positives for nested
test() detection, breaking previously working tests with "test() inside
another test() is not yet implemented" errors.

Pinning to 1.2.22 until this regression is fixed.

oven-sh/bun#5090

Author: dahlia

.github/workflows/main.yaml

@@ -136,7 +136,7 @@ jobs:
         run_install: true
     - uses: oven-sh/setup-bun@v2
       with:
-        bun-version: latest
+        bun-version: 1.2.22
     - run: pnpm run -r test:bun
 
   check:

mise.toml

@@ -1,5 +1,6 @@
 [tools]
-bun = "1.2"
+# Bun version should be kept in sync with GitHub Actions workflows
+bun = "1.2.22"
 deno = "2.3"
 node = "24"
 "npm:pnpm" = "latest"