ci(gitea): run CI in a prebuilt PHP image instead of setup-php bootstrap

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AqpXh3hQMMaC74pTjFq4it

tools/gitea-pipeline/render.py

@@ -12,6 +12,9 @@ import json
 import sys
 
 A = "https://git.protopeer.com/peptide-repo/peptide-e2e/.gitea/actions"
+# CI image with PHP 8.1/8.2/8.3 + Composer preinstalled (peptide-e2e/ci-image).
+# Without it setup-php bootstraps a compiler toolchain on every job (5-20 min).
+CI_IMAGE = "git.protopeer.com/peptide-repo/ci-php:2026-10"
 DEFAULTS = {"tests": "stubs", "has_js": False, "line_limit_paths": "includes",
             "enforce_300": True, "phpcs_autofix": True, "audit": True,
             "php_versions": ["8.1", "8.2", "8.3"], "extras": []}
@@ -24,10 +27,8 @@ EXTRAS = {
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: shivammathur/setup-php@v2
-        with:
-          php-version: '8.1'
-          coverage: none
+      - name: Use PHP 8.1 (preinstalled in the CI image)
+        run: update-alternatives --set php /usr/bin/php8.1 && php -v | head -1
       # Fails if any PRAUTOBLOGGER_* constant referenced in shipped PHP is neither
       # defined in prautoblogger.php nor guarded by defined() (v0.19.0 incident class).
       - run: php scripts/check-constants.php
@@ -244,7 +245,9 @@ jobs:
         with:
           token: ${{{{ secrets.GITHUB_TOKEN }}}}
 """)
-    return "".join(out)
+    return "".join(out).replace(
+        "    runs-on: ubuntu-latest\n",
+        f"    runs-on: ubuntu-latest\n    container: {CI_IMAGE}\n")
 
 
 if __name__ == "__main__":