Add development environment and workflow section

Add edit instructions for AGENT.md file

AGENT.md

@@ -1,6 +1,9 @@
 ## Philosophy
 Minimal PHP for modern conveniences. Prioritize longevity (decade-scale maintainability) by avoiding volatile dependencies. Strictly add only what's essential—readable, simple, and future-proof.
 
+## Edit instructions
+All edits to this AGENT.md file should be done in a compressed shortform for LLM consumption.
+
 ## Core Constraints
 **Minimalism:** Only essential tech (HTML, PHP 8.4+, CSS). No JS, frameworks, build tools, or package managers. Comments only for major sections.
 
@@ -20,3 +23,12 @@ Minimal PHP for modern conveniences. Prioritize longevity (decade-scale maintain
 **CSS:** Variables, native nesting, grid layouts. `clamp()` over `@media`. Relative units > pixels.
 
 **Templates:** Escape output (`htmlspecialchars()` for UGC). Short echo tags (`<?= $var ?>`).
+
+## Development Environment and workflow
+**LLM Agent Testing Protocol:**
+**Container isolation:** ALL test data (CSV, temp files, generated content) MUST remain inside container filesystem (not mounted volumes)
+*Testing website:** `curl localhost:4040/path` to fetch pages, test forms with `curl -X POST -d "field=value" localhost:4040/path`
+- **Test data paths:** Use `/tmp/` or `/var/test/` inside container—never write to `/var/www/html` or mounted dirs during tests
+**Running tests:** `podman exec stopplidelsen.no php /path/to/test.php` or `podman-compose run --rm custom php /tmp/test-script.php`
+ **Syntax checks:** `podman exec stopplidelsen.no php -l /var/www/custom/file.php`
+ **Cleanup:** `podman-compose down && podman-compose up -d` between test runs