ci(release): replace box with bin/build-phar.php

Box (humbug/box) was the previous PHAR compiler. Removed it in favor
of the internal bin/build-phar.php which:
  - Needs no external tool installation (saving ~5s + wget overhead)
  - Needs no composer install (autoloader is generated inline)
  - Produces a PHAR in <0.1s instead of 50s+
  - Outputs 0.03 MB instead of ~30 MB

Previous flow:
  wget box.phar → composer install → box compile --config=box.json

New flow:
  php -d phar.readonly=0 bin/build-phar.php

Author: walmir-silva

.github/workflows/release.yml

@@ -23,19 +23,9 @@ jobs:
           ini-values: phar.readonly=0
           tools: composer:v2
 
-      - name: Install humbug/box
-        run: |
-          wget -q -O box https://github.com/box-project/box/releases/latest/download/box.phar
-          chmod +x box
-          sudo mv box /usr/local/bin/box
-          box --version
-
-      - name: Install dependencies
-        run: composer install --no-interaction --prefer-dist --optimize-autoloader
-
       - name: Compile PHAR
         run: |
-          php -d phar.readonly=0 box compile --config=box.json
+          php -d phar.readonly=0 bin/build-phar.php
           ls -lh build/kcode.phar
 
       - name: Verify PHAR