Stdlib: fopen, fwrite, fclose, and file_put_contents for templates and logs

[PurHur]

Problem

Small PHP apps read/write files for HTML templates, config, and logs. Today only VM host calls file_get_contents in bin/serve.php; user PHP has no fopen/file_put_contents in the compiler stdlib.

#62 covers file_get_contents; #171 covers streaming via readfile.

Goal

Implement a minimal, safe file I/O subset for web apps (read/write text files under a configurable root).

Tasks

• VM builtins: fopen, fread, fwrite, fclose, file_put_contents, file_exists, is_file, is_dir
• Resource type in VM (Variable::TYPE_RESOURCE) or simplify to path strings + internal handles
• JIT/AOT: start VM-only; document in capability matrix
• Optional docroot jail: paths must resolve under project public/ or phpc.json root (DevEx: phpc.json project manifest (entry, includes, public assets) #106)
• PHPT: write log line, include template file
• Error modes: @ suppression, warnings on missing file

Acceptance criteria

file_put_contents(__DIR__ . '/cache/hit.txt', 'ok');
echo file_get_contents(__DIR__ . '/cache/hit.txt');

Runs in VM; JIT/AOT documented as follow-up.

Dependencies

• Language: Magic constants __DIR__, __FILE__, __LINE__ for multi-file apps #85 __DIR__ for multi-file apps
• DevEx: phpc.json project manifest (entry, includes, public assets) #106 phpc.json paths
• Stdlib: file_get_contents and readfile for templates/assets #62 file_get_contents

Files

• ext/standard/ new modules, lib/VM.php, docs/capabilities.md