php-transformer: resolve nested telemetry script targets

[chubes4]

Summary

• Resolve source script paths relative to their owning source document before telemetry self-target classification.
• Add contract coverage for a nested entrypoint whose telemetry script reads its own script tag.

Verification

• php php-transformer/tests/contract/run.php
• php php-transformer/tests/parity/run.php

AI assistance

• AI assistance: Yes
• Tool(s): openai/gpt-5.5 via OpenCode
• Used for: diagnosing the nested telemetry self-target false positive, implementing the focused fix, and running verification.