feat(php): add call hierarchy

[sidux]

Summary

• add standard prepare, incoming, and outgoing Call Hierarchy handlers for PHP functions and methods
• reuse the existing Find References and Go to Definition pipelines instead of adding a second resolver
• group incoming call sites by their containing callable and deduplicate outgoing targets
• remove the completed Call Hierarchy roadmap item

Why

Editors already expose the LSP Call Hierarchy UI, but PHPantom did not advertise or answer it. Reusing the existing semantic pipelines keeps hierarchy results consistent with navigation, aliases, inheritance, and future type-engine improvements. It also provides the standard extension point used by higher-level event metadata without putting framework logic into ordinary PHP call resolution.

Validation

• cargo test call_hierarchy --lib
• cargo clippy -- -D warnings
• cargo fmt
• full stacked suite: cargo test --all-targets (14,286 passed, 2 ignored)

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 96.27832% with 23 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/call_hierarchy.rs	96.27%	23 Missing ⚠️

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[AJenbo]

Thanks